Patented Sept. 17, 1946 2,401,651 UNITED s'rArEs PATENT OFFICE‘ 2,407,651 CONCENTRATING FLUORSPAR BY FROTH ' FLOTATION Julius‘ Bruce Clemmer and Ballard H. Clemmons, Tuscaloosa, Ala., assignors to the United States of America, as represented by the Secretary of Interior No Drawing. Application November 1, 1944, Serial No. 561,458 18 Claims. (Cl. 209-166) (Granted under the act of March 3, i883, as amended April so, 1928; 370 o. G. 757) 2 The invention described herein may be manu factured and used by or for the Government of Fluorspar deposits occur in both igneous and sedi the United States for governmental purposes or shear zones; as horizontal or bedding replace ment deposits in sedimentary rocks; or as in without the payment to us of any royalty thereon . in accordance with the provisions of the act of April 30, 1928 (Ch. 460, 45 Stat. L. 467). mentary rocks as veins following faults, ?ssures, crustations in vugs and caves. Sizeable deposits of ?uorspar are known in our Western States This invention relates to an improved process including California, Arizona, New Mexico, Ne for the concentration of ?uorspar ores by froth vada, Texas, and Colorado. The vein and bedded ?otation; more particularly it relates to the froth deposits of the Il1inois~Kentucky district are re ?otation of ?uorspar of a high degree of pur 10 puted to be the largest in the world. It is to ores ity from pulps containing calcite or barite. from these deposits that particular attention was An object of the invention is to provide a froth given in developing the improved process of froth ?otation process for the concentration of natural ?otation hereinafter described, although ores ?uorspar ores and products for recovery of ?uor from other localities can successfully be bene spar. A further object is to provide an improved 15 ?ciated by our invention. ?otation process for separating ?uorspar from The gangue minerals commonly found asso calcareous gangue materials such as calcite or ciated with ?uorspar in commercial deposits are limestone. A still further object is to provide a quartz, calcite, and barite. Other accessory min ?otation process for recovering ?uorspar of a erals may include various sul?des such as galena, high degree of purity from ores containing barite. 20 sphalerite, pyrite, or chalcopyrite, or oxidized lead Still other objects include the development of an and zinc minerals such as cerussite and smith improved ?otation process which will have greater sonite. Common gangue constituents of ?uor selectivity in separating ?uorspar from associ ated sul?de or non-sul?de gangue materials and spar ores are limestone and clay and many ores also contain shale and sandstone. Ores from dif thereby effect greater operating economies. 25 ferent deposits, or from different portions of the ‘ ,Other objects, purposes, and advantages of the ‘invention will hereinafter more fully appear or same deposit, may show considerable variation both as regard mineral association and relative will be understood from the detailed description proportions of ?uorspar and other minerals. In of its practice. the Illinois-Kentucky ?uorspar district, for ex Fluorspar has wide and varied application in 30 ample, the ore from a particular deposit may be the chemical, ceramic, and metallurgical indus devoid of barite whereas that from an adjacent tries. Its uses range from a source of ?uorine and hydro?uoric acid in chemical. processes to that of a ?uxing material in steel making. Commercial deposit may contain 10 percent or more of barite. Similarly, the galena or sphalerite contents‘may also show considerable variation. Ore from a ?uorspar, commonly referred to as "Spar," is 35 particular mine location may contain minute furnished to meet a number of varying speci?ca quantities of galena or sphalerite whereas ore tions as to size and analysis. The ?uorspar con from another part of the mine often contains tent of the commercial products ranges from sufficient galena or sphalerite to justify their re a minimum of 85 percent in the case of “gravel covery as valuable by-products in ?uorspar mill spar” for steel making to a minimum of 97 per 40 ing. The lime and silica contents of ?uorspar cent ?uorspar in “acid grade” material for chem ores may likewise show considerable variation. ical processing. The speci?cations as to allow Uniform deposits of ?uorspar are an exception able impurities vary with the industry, but all rather than the rule, and milling methods must demand a ?uorspar product relatively free of be sufficiently ?exible to permit treatment of a silica, calcium carbonate, barite, and sul?des such 45 variety of ores of different grades and mineral as galena, sphalerite, or pyrite. Flourspar ores as association. An important object of this inven mined seldom meet market speci?cations, either tion is to provide for the?rst time a ?otation as regard ?uorspar content or freedom from im purities, and suitable methods of concentration, method applicable to a variety of ores of different grades and mineral association for recovery of such as froth ?otation, must therefore be em 50 the ?uorspar from associated gangue materials. ployed to recover commercial products from the As a result of extended research and experi low grade or contaminated ores. mentation, we have discovered that the lignin Geographically, ?uorspar is widely distributed sulphonates used in conjunction with an addition in minute quantities, but deposits of commercial agent, such as sodium ?uoride, are effective for value in the United States are not numerous. 65 the retardation of barite and siliceous or cal 2,407,651 - 3 4 careous gangue materials in the froth ?otation of ligneous materials. The precipitated lignin sul phonate may be further puri?ed by dissolution ?uorspar by-fatty acid or soap collecting agents. The combination of these reagents also enables retardation of sul?de minerals such as galena. sphalerite, or pyrite when ?oating ?uorspar from pulps containing the minerals as gangue. Oxi dized ore minerals and iron oxides, or other non sul?de gangue minerals such as celestite, may also be retarded in ?uorspar ?otation by these de pressants. Fluorspar concentrates of high purity have been recovered from a wide variety of ?uorspar ores and products even when containing sul?de and non-sul?de gangue materials, by using lignin sulphonates and addition agents to selec tively retard the gangue materials while floating the ?uorspar with fatty acid collecting agents. The lignin sulphonates which we prefer to and re-precipitation, by dialysis, or other methods. The puri?ed sulphonates are ordinarily marketed as the powdered forms but solutions containing from 15 to 50 percent of the lignin sulphonate are also available. Various of the commercially available puri?ed lignin sulphonates including the calcium, magnesium, sodium, barium, aluminum, zinc and copper salts have been tested and found satisfactory as gangue depressants in our method of ?uorspar ?otation when used in conjunction with an addition agent such as sodium ?uoride. The calcium, magne sium, and sodium sulphonate are less expensive than the heavy metal salts and are preferred. ' The purified sulphonates are somewhat more effective than the crude or unpuri?ed compounds utilize as gangue depressants ‘in this invention but all of the liquid or powdered forms of either are present in and may be derived from the by product of the sul?te process of paper making 20 the crude or puri?ed sul?te liquor materials may be used in our method of ?uorspar ?otation and commonly known as “sul?te liquor.” These the ultimate choice of the particular material liquors separated as waste from the cellulose pulp employed will largely depend upon economic contain soluble salts of the lignin sulphonic acids factors. and other non-ligneous organic substances, such The lignin sulphonates are recognized as being as hydrolyzed carbohydrates. resulting from de 25 multi-basic in character and contain acidic groups composition of the wood by the acid solutions used of varying strength ranging from the strong sul in the pulping process. In the sul?te process, the phonic to the weak phenolic group, and some may lignin in the wood is dissolved by digesting the wood chips with an acid solution of calcium, magnesium, or sodium sul?te at an elevated tem also contain minor amounts of carboxyl groups. 30 The sulphonic is the dominant acidic group and the amount depends on the degree of sulphoniza tion employed in the pulping process to solubilize the lignin and allow its separation from the cel ing on the base employed. The sul?te liquors con lulose. Lignin sulphonates of either higher or taining the lignin sulphonates and non-ligneous materials may be used as the gangue depressants 35 lower degree of sulphonation may be made by re treatment of the sul?te liquors to meet speci?c in our method of ?uorspar ?otation or the crude requirements. The lignin sulphonic acids readily sul?te liquors may be puri?ed by known methods react with metal salts to form the corresponding to reject the non-ligneous substances and recover sulphonates. These salts may be made from the a substantially puri?ed lignin sulphonate which may be employed to retard the gangue. 40 calcium salt by double decomposition reactions or from a solution of the free sulphonic acid. The crude or whole sul?te liquor recovered The type of salt formed depends on the conditions from the sul?te pulping process and containing perature wherebythe lignin forms soluble calcium, magnesium, or sodium lignin sulphonates depend the lignin sulphonates and non-ligneous organic established for the reaction. In the normal or so-called acid salt at pH of about 5 in aqueous solution only the strong sulphonic groups are in their salt form; in the so-called neutral salts at about pH 7.0, the sulphonic and some of the phenolic groups are in salt form; and in the so stantially dehydrated. The liquid and powdered called basic salts at pH 11 and above all the acidic forms have been used interchangeably in our 50 groups may be regarded as present in their salt form. The basic calcium salts are insoluble in ?otation and, based on their respective content of aqueous solutions at high pH but disperse or dis lignin sulphonate, are equally effective for re tardation of gangue constituents. Comparative solve under neutral or acid conditions. Other wise all lignin sulphonates of normal degree of ?otation tests using the calcium, magnesium, and‘ sodium base sul?te liquors or dehydration resi 55 sulphonation are soluble inv water under all pH dues gave substantially equivalent results. The conditions to give colloidal solutions or dispersions non-ligneous materials present in the liquid or which we may use as gangue depressants in con dehydrated residues appear to be an inactive junction with addition agents such as sodium diluent and exerts little or no deleterious effect in ?uoride in our method of ?uorspar ?otation. the froth ?otation of ?uorspar when using sodium 60 A variety of liquid and powdered forms of substances, such as hemi-cellulose and various sugars, may be evaporated to yield a concentrated liquid or dehydrated residue for marketing. The liquid forms as marketed contain about 50 per cent water whereas the powdered forms are sub ?uoride as an addition agent. Pound per pound, both crude and puri?ed sul?de liquid products the evaporated crude sul?te liquors or dehydra are commercially available and have been found satisfactory gangue depressants in the practice of this invention. Examples of the sul?te liquor tion residues are slightly less effective than the corresponding puri?ed lignin sulphonates rela tively free of non-ligneous material, but are par ticularly attractive as gangue depressants in our method of ?uotation due to their lower cost. The crude .or evaporated sul?te liquors may be processed by numerous methods to reject the non ligneous material and recover substantially puri ?ed lignin sulphonates. Fractional precipitation methods using sodium chloride, calcium chloride, 65 materials which we have used successfully in clude those sold under the trade names “Bindarene liquid,” “Binderene ?our,” “Goulac,” “T. D. A.,” "Marathon extracts M, T, NS, TanC, I SL, DT-31, DT-32, DT-33, DT-34, and DT-35," 70' and the “Daxads 11, 21, and 23.” Other sul?te liquor products which have been found accept able include the crude and puri?ed magnesium lignin sulphonates, the acid, neutral, and basic mineral acids, lime water, basic lead acetate, or calcium lignin sulphonates, and sodium, copper, organic bases may be employed to recover the lignin, sulphonate and reject the bulk of the non 75 zinc, aluminum, and barium lignin sulphonates. 5 9,407,651 As far as we are aware the lignin sulphonates singly or together with addition agents such as sodium ?uoride have not heretofore been em ployed for the retardation of gangue constitu ents in the ?otation of ?uorspar ores. In our method of froth ?otation of ?uorspar, retarda tion of the calcite and barite or other gangue constituents is sought and the quantities of lignin sulphonate employed must be su?icient to re . 6 . _ tively freeof soluble salts or slime gangue con stituents. We prefer to use addition agents such as sodium ?uoride in conjunction with the lignin sulphonates for the ?otation of ?uorspar from all ?uorspar ores. Less collector is required and ?otation of the ?uorspar is more rapid and com plete. Sodium ?uoride was the preferred addition' agent used in conjunction with the crude or tard these constituents. The quantity of lignin 10 puri?ed lignin sulphonates. Ammonium and potassium ?uoride were found equally effective sulphonate required varies with di?erent ores and may be as little as 0.25 to as much as 5 pounds or more per ton of ore; the optimum but was less attractive due to their higher cost. must be determined by trial. The mechanism of the retarding action of the lignin sulphonates on gangue minerals in our 15 method of ?uorspar ?otation has not been de? nitely determined and this invention is not lim were also satisfactory but had no particular ad Aluminum ?uoride and sodium silico~?uoride vantage over sodium ?uoride and were some what less soluble. Hydro?uoric and hydro?uo silico acids may also be used if desired. Our tests indicate that any inorganic ?uorine-bear lIlg compound which ionizes in aqueous solution ited to any theory of action. It seems probable however, that an important effect of the sul to yield the ?uoride ion may be used as addition phonates is to coat the surfaces of the gangue 20 agents in our method of ?otation. particles so that they present water-avid sur "Addition agents, other than the ?uorides, faces which prevents their attachment to the which we have used in conjunction with the. bubbles in froth ?otation. The lignin sulphonate lignin sulphonates to obtain more effective re coating on the gangue may be induced as a re tardation of the gangue in ?uorspar ?otation in sult of either chemical reaction or adsorption to 25 clude sodium sul?de, sodium sul?te and hydro satiate the surfaces, and this coating prevents sul?te, sodium cyanide, potassium dichromate. or greatly inhibits formation of collector coat ammonium acetate, potassium ferro and ferri ings which normally would, have formed to cyanides, sodium citrate, sodium meta and per render the particles ?oatable. It may be fur borates, borax, soda ash, caustic soda, and so 30 ther assumed that ?uorspar particles in the pulp dium silicate. These reagents are less effective exhibit ‘much less tendency than the gangue than the ?uorides but may be advantageously particles to become coated by the lignin sul employed on ?uorspar ores to yield an improved phonates, and, as a consequence, the unsatiated separation. These reagents serve a multi-fold ?uorspar surfaces become collector-coated and purpose and assist in ?otation by complexing or 35 are thus rendered ?oatable. J-udicious use of precipitating soluble salts in the pulp, establish the lignin sulphonates thus enables selective the optimum pH for ?otation, or aid in proper retardation of the gangue in ?uorspar ?otation. dispersion of slime gangue constituents. Soda The bene?cial effect of addition agents such ash, caustic soda, sodium cyanide, and sodium as sodium ?uoride in the ?otation of ?uorspar silicate are particularly advantageous as auxil when using the lignin sulphonates as gangue 40 iary pH modi?ers, pulp conditioners, and slime depressants was apparent in the testing of a dispersants in conjunction with an inorganic variety of ores containing barite or calcareous ?uoride in our method of ?otation. gangue materials. Use of the ?uorides enabled our method of ?otation we have found that more rapid and complete ?otation of the ?uor 45 theInpulp should be dispersed. The lignin sul spar and more e?ective retardation of the gangue phonates and the ?uoride addition agents which constituents. The mechanism by which the we employ in our method of ?otation serve the ?uorides accomplish these bene?cial effects is two-fold purpose of dispersing the pulp and not de?nitely known and no limitation to any retarding the gangue materials. Supplemen particular theory of action is intended in this tary dispersing agents are seldom required as patent. It seems likely however that one of the suf?cient lignin sulphonate and soluble ?uoride important functions of the ?uoride is to com to depress the gangue constituents in ?uorspar plex or precipitate soluble salts in the pulp ?otation adequately disperses the ore pulp. which would otherwise impair selectivity of the Supplementary slime dispersing agents, such as separation. The ?uorides are effective slime silicate, may be advantageously used on dispersants and may aid ?otation by assisting 55 sodium ?uorspar ores containing large amounts of clay. in the proper dispersion of the pulp. The com Various organic dispersants including the tannin bined effect of complexing soluble salts and dis extracts, such as quebracho, chestnut, oak, or persion of the slime may possibly serve to clean Borneo cutch, and the dextrins, starches, and the surfaces of the ?uorspar particles to make gums may also be used to supplement the lignin them more readily ?oatable by the fatty acid 60 sulphonates and enable reduced quantities to collectors. Similar cleaning of the gangue be employed. The tannin extracts are particu particles renders them more susceptible to larly helpful on those ores containing large quan retardation by the lignin sulphonates. These titles of calcite as they assist in the retardation factors may be effective in varying degree on of this contaminant. The quantity of tannin different ores depending upon the soluble salts 65 used in conjunction with the lignin sulphonate present and the relative proportions and surface must be carefully controlled as an excess tends purity of the ?uorspar and gangue minerals. We to retard the ?uorspar. have discovered that the ?uorides are particu We have achieved good ?otation of ?uorspar larly advantageous and their bene?cial effect is more marked when treating ores containing sol 70 from both neutral and moderately alkaline pulps by the practice of this invention. Precise con uble salts or large amounts of calcite or barite. trol of the pH of the pulp is not essential for The need for the ?uorides is less apparent and an effective separation but we‘ prefer that the they may be omitted if desired, in the ?otation of ?uorspar from the highly siliceous ores rela 75 pH be maintained in the range 8 to 10.0. The frothing proclivities of the fatty acid and soap 2,407,651 7 sulting from the cleaning operations may be re jected as waste or returned to the preceding ?o tation step of other convenient points in the pulps of pH 11 or more should be avoided as the ?otation or grinding circuit for retreatment. voluminous froths are di?icult to control. A pulp The practice of this invention is not limited to pH'of 8 to 10 gave compact, heavily mineralized 5 any particular order of addition of the separate ?uorspar froths on a variety of ?uorspar ores reagents. We prefer however to properly condi containing barite and siliceous or calcareous tion the ore pulp with the lignin sulphonate and gangue materials. We have found in many cases sodium ?uoride, or other addition agents, before that the combination of sodium ?uoride and a lignin sulphonate' gave a pulp of suitable pH 10 adding the ?uorspar collecting agent. ,The de pressants and pH modifying agents, singly or to without the addition of any other pH modifying gether, may be added to the grinding step if de agent. A pulp of too high pH may be corrected sired. Our tests indicate that moderate condi by judicious addition of an inorganic acid to tioning of the pulp with the depressants ensures lower the pH within the optimum range and, conversely, a pulp of too low pH may be corrected 15 maximum retardation of the gangue constitu collecting agents increase progressively with in crease in pH of the pulp and strongly alkaline by addition of a proper amount of an alkaline reagent such as soda ash, caustic soda, or sodium ents. Likewise, moderate conditioning with the silicate. The pH modifying agent may be added to the pulp at any time before completion of the ?uorspar. simultaneously with the lignin sulphonate and tion, and the proper quantities are best deter sodium ?uoride. The fatty acid and soap collecting agents have been found suitable for ?otation of the ?uorspar in the practice of this invention. The collectors 25 case. We have found the invention applicable to a wide variety of ?uorspar ores containing collecting agent ensures maximum collection of ' The proportions of the several reagents used in the ?otation, but we prefer to add it prior to or 20 this invention are subject to considerable varia mined by experimentation for any particular barite and siliceous or calcareous gangue ma a variety of ?uorspar ores containing barite and terials. Extensive ?otation experiments on ?uor spar ores from domestic and foreign deposits calcareous or siliceous gangue constituents in- ~ have demonstrated that the invention is par which have been used in the ?otation testing of ticularly advantageous in that it enables recovery ?sh oil soap, ?sh liver oil fatty acids, and tallv 30 of high-grade ?uorspar concentrates from ores clude crude and puri?ed oleic acid, sodium oleate, oil. Saponi?ed tall oil and sulfate soap or skim mings derived from sulfate paper mill black liq ors may also be used provided the quantities are which heretofore had been difficult or impossible to treat by known methods. A proper balance of the lignin sulphonate and sodium or other soluble ?uoride effectively retards the gangue and en carefully controlled. The crude tall oil and sul fate soap products are violent frothers and an 35 ables rapid and complete ?otation of the ?uor spar with moderate quantities of fatty acid' col excess should be avoided. lecting agents. Excess of collecting agent or de In carrying out the ?otation process according ?ciency of the depressants results in an inferior to this invention, the ?uorspar ore or product separation and the proper quantities must be de to be treated is ground to proper size for ?otation, if not already of such size, by conventional meth 40 termined by trial. Moderate variation of the col lector and depressant reagents is permissible on ods. The ?neness of the grind may vary from 20 to 200 mesh or ?ner depending on the locking many ores however. The wider latitude in re characteristics of the particular material; sub stantially complete liberation of the ?uorspar agent control and more effective retardation of gangue constituents accomplished by this inven selected accordingly. heretofore difficult to treat. from the gangue is essential for a satisfactory 45 tion thereby effect greater operating economies vand facilitate recovery of ?uorspar from ores separation, and the ?neness of grind should be The ground material in _ ~ This invention is applicable to ?uorspar ores the form of a pulp is then subjected to froth and products containing associated sul?de min ?otation to recover the ?uorspar and reject the gangue materials in the following manner: The 50 erals such as galena or sphalerite. Those ores containing sufficient sul?de minerals to warrant pulped material is conditioned with a sul?te their economic recovery may best be treated by liquor material containing lignin sulphonate; an customary sul?de ?otation methods to ?rst re addition agent such as sodium ?uoride; and a cover the sul?des and the resulting tailings may fatty acid collector agent such as oleic acid. Also if desired a pH modifying agent and slime dis 55 then be retreated by this invention to recover the ?uorspar and reject the gangue. We have persant agent may be used. The conditioned found that the reagents customarily used for the ?otation of sul?de minerals do not interfere with the subsequent ?otation of ?uorspar by our ?uorspar froth and a tailings product essentially free of ?uorspar and containing the gangue ma 60 method. The lignin sulphonates adequately re tard the remaining sul?des as well as barite, terials. The froth product may contain some calcite, or other gangue materials and permits quartz calcite, barite, or other gangue materials recovery of high-grade ?uorspar concentrates collected with the ?uorspar in the initial froth essentially free of these impurities. Met'al salts lng operation. The froth is repulped with addi tional water and re?oated to recover the ?uorspar 65 in the ?uorspar feed carried through from the sul?de ?otation step, wherein salts such as cop and reject the remaining gangue materials. One per or zinc sulfate were employed as activators or more such cleaning steps suffices to yield ?nal or depressants, may if desired, be overcome by ?uorspar concentrates of the desired commercial conditioning the sul?de tailings with sodium cy grade. Additional reagents, such as a small quantity of the lignin sulphonate, may be used 70 anide prior to ?otation of the ?uorspar by this invention. The cyanide complexes or precipi in the cleaning operations to facilitate rejection tates the metal salts and thus overcomes any of the gangue impurities. Also if desired, a froth deleterious effect these salts may exert in ?uor— agent such as pine oil or an alcohol may be spar ?otation. Sodium or other soluble ?uoride used to promote complete and more rapid ?ota tion of the ?uorspar. The tailings material re 75 is also effective for overcoming the deleterious pulp is then froth ?oated by customary mechani cal or pneumatic methods to yield an enriched 2,407,051 effect of metal salts and complements the action of sodium cyanide. Our methodis also effective for recovering acid grade ?uorspar directly from ore pulps contain ing substantial quantities of galena, sphalerite. sentially free of gangue material. The froth was collected for 2.5 minutes when ?otation was completed. The rougher froth was triple cleaned by re?oating in the same cell using tap water ~ or pyrite as gangue constituents. Recovery of 5 and 0.08 pound per ton of lignin sulphonate in each step to further retard the gangue collected acid grade- ?uorspar can thus be effected by our with the ?uorspar in the roughing operation. method not only when the pulp treated is sub stantially free of metallic sul?des but also when The ?nal ?uorspar concentrates represented a the sul?des are present in material amounts and 10 weight recovery of 55.6 percent, assayed 98.2 per cent CaFz, 0.1 percent CaCOa, 0.8 percent SiOz, it is also substantially immaterial whether a large or small amount of barite or calcite is pres ent. Our method is therefore particularly ad and 0.7 percent'Rzoa, and accounted for a recov . ery of 98.8 percent of the ?uorspar in the ore. The high recovery of acid-grade ?uorspar'in' type found in the Illinois-Kentucky ?uorspar area 15 the test demonstrated the‘utility of the magne sium lignin sulphonates for ‘retarding siliceous containing galena and sphalerlte associated with gangue materials in ?uorspar ?otation. Calcium the ?uorspar together with extremely variable or sodium lignin sulphonates gave substantially amounts of barite calcite, or siliceous gangue con vantageous for ‘the concentration of ores of the stituents. ‘ As a result of the practice of this invention, rapid and essentially complete ?otation of ?uor 20 spar may be effected from ore pulps containing sul?de and non-sul?de gangue constituents with the same results. Combinations of sodium ?uo ride and crude or puri?ed lignin sulphonate were even more effective and gave a higher recovery of ?uorspar in concentrates of lower silica con tent. A duplicate of the recorded test using 1.0 pound of sodium ?uoride per ton in addition to out the necessity of desliming Desliming of the ?otation feed is not obligatory in our method of 25 the magnesium lignin sulphonate yielded a ?nal ?uorspar concentrate which assayed 98.6 percent ?otation but maybe desirable when treating sur CaFz, 0.1 percent CaCOa, 0.6 percent S102, and face ores containing large amounts of clay or 0.5 percent R203, and represented a recovery of top-soil as contaminants. Less collector is re 97.6 percent of the ?uorspar. quired and the quantities of the lignin sulpho~ The results of the above mentioned tests were nates and sodium ?uoride may be materially re duced when ?oating ?uorspar from deslimed 30 representative of those obtained on other sili ceous ?uorspar ores from deposits in Arizona, pulps. New Mexico, and Montana. Quartz, feldspar Anderson et al., in U. S. Patent 2,263,552 pro and other silicate minerals including clay, and posed the use of “soft" water, i. e. one having not associated iron oxides were readily retarded by to exceed 5 grains of hardness, to obviate neces-V 35 the lignin sulphonates alone or preferably in sity of desliming in the ?otation of ?uorspar ‘combination with sodium ?uoride and enabled a from calcareous gangue materials. We have now good recovery of the ?uorspar in acid-grade con discovered that neither desliming nor a soft Wa centrates by fatty acid or soap collectors. ter is obligatory in our method of ?uorspar ?ota tion. Although we prefer to use a soft or only 40 Example II moderately hard water in ?otation, we have suc A tailing pond material from a gravity con cessfully used water containing as high as 20 grains of hardness without seriously impairing centration plant operating in the Southern llli nois ?uorspar district was next examined. The material consisted of ?uorspar associate-d with crease with increase in hardness of water em 45 both siliceous and calcareous gangue constitu ents and assayed 43.1 percent CaFz, 35.4 percent ployed and operating economy suggests that hard CaCOz, and 18.2 percent SiO2. Grinding to 48 water be pro-treated by either lime soda or zeo mesh was su?icient to liberate the ?uorspar for ‘ lite processes prior to use, The invention will be further illustrated but is 50 recovery of acid grade ?uorspar concentrates. Numerous ?otation tests were made on this not intended to be limited by the following exam sample using various of the commercially avail ples in which parts and percentage compositions able liquid and dehydrated residues of crude and are by weight unless otherwise designated: puri?ed sul?te waste liquors containing lignin Example I sulphonates, with and without sodium ?uoride A ?uorspar ore consisting essentially of ?uor 55 to retard the gangue while ?oating the ?uorspar with fatty acid collectors. The lignin sulpho spar associated with a siliceous gangue composed nates while satisfactory, were less effective than predominately of quartz and clay was obtained the combination of depressants for retarding cal from a Colorado deposit. A head analysis gave cite and limestone and close control of the col 57.8 per cent CaFz, 0.7 percent CaCOz, 29.2 per cent S102, and 6.2 percent R203. A representa 60 lector was essential for a satisfactory separation. A typical test using the equivalent of 1.0 pound tive portion of the ore was wet-ground to 48 per ton of substantially pure magnesium lignin mesh in a laboratory ball mill and the pulp, in sulphonate as the depressant and 0.64 pound of cluding slime, was transferred to a, laboratory commercial oleic acid per ton as the collecting mechanical ?otation cell of standard design. Su?icient tap water was added to give a slurry ()5 agent yielded a froth product in the roughing operation which assayed 76 percent CaFz, 20 containing about 20 percent solids for ?otation. percent CaCOz, and 2 percent S102, and con The pulp was conditioned for 5 minutes with the tained about 75 percent of the ?uorspar in the equivalent of 1.0 pound per ton of a magnesium ?otation feed. Triple-cleaning of the rougher base lignin sulphonic acid and 0.8 pound per 7o froth gave a ?nal ‘?uorspar concentrate of acid ton of red oil (commercial oleic acid) was then grade assaying 98.0 per cent CaFz, 1.1 percent added and the pulp conditioned for an additional CaCOe, and 0.2 percent SiOz, and represented a 2.5 minutes. Air was then allowed to enter the recovery of 59.3 percent of the ?uorspar. Sub cell and resulted in an immediate formation of a stantially equivalent results were obtained with compact, heavily mineralized ?uorspar froth es 75 calcium and sodium salts of the lignin sulphonic selectivity of the separation on many ?uorspar ores. Collector requirements for ?otation in 12' acids. The crude'lignin products from ‘partial or complete dehydration of the whole‘ sul?te liquors while entirely-operativalwere less e?ective than the puri?ed sulphonates for retarding calcareous ' gangue and closer control of the collector was es sential 'for separation of ?uorspar in concen ‘V - ' Flakes." The pH of the pulp was 11.0 which . exceeds the optimum desired for ?uorspar ?ota, tion. Sulfuric acid equivalent to 0.6 pounds per ton of feed, was then added to reduce the pH of the pulp to 8.6, a more desirable value. Mas nesium lignin sulphonate and oleic acid, equiv alent to 1.0 and 0.32 pounds per ton, were added‘ and the pulp conditioned an additional 5 min The combination of. a lignin sulphonate and utes. Air was then admitted to the cell and re sodium ?uoride was found particularly advan tageous on the tailing pond material. Less 10 sulted in the immediate formation ‘of a heavily mineralized ?uorspar froth. The froth was col collector was required and ?otation of’ the ?uor lected for‘ 3_minutes when ?otation was com spar was more rapid" and complete. Uniformly pleted. The froth assayed 77.1 percent CaFz, and good results were ‘obtained with either the crude accounted for 91.5 percent of the ?uorspar-in the . or puri?ed lignin sulphonates used in conjunc tion with chemically. .pure or insecticide-grade 15 feed. Triple-cleaning of the rougher froth with an additional 0.08 pound per ton of ‘magnesium sodium ?uoride. A proper balance of the collec lignin sulphonate in each cleaner ‘yielded a ?nal tor and depressants had to be determined by trial, ?uorspar concentrate of the grade and recove but moderate variation of the quantities of col indicated above. ~ lector, sodium ?uoride, or lignin sulphonate was Soda ash, caustic soda, and sodium silicate 20 were used in conjunction with the combination ‘ A typical test on the tailing ‘pond material of ?uoride and lignin sulphonate in other tests ground to 48 mesh in a laboratory ball mill and ?oated by the procedure described in Example I ' on the tailing pond material to establish the optimum pH for ?otation and to assist in dis~ using 1.0 pound per ton of insecticide-grade so-. dium ?uoride and sodium lignin sulphonate, re 25 persion of the ore pulp. These reagents were also helpful as a water conditioner ‘and their spectively, in conjunction with 0.32 pound per ton’ of crude oleic acid as the ?uorspar collector a use enabled hard water to be employed in ?ota tion without impairing selectivity of the sepa yielded a rougher froth containing 92 percent of the ?uorspar in the feed and assayed about 75 percent CaF-z, 20 percent CaCOa, and 3 percent 30 Tap water of moderate hardness was used in all of the ?otation tests previously described. A SiOa. Triple cleaning of the rougher froth with number. of tests were also made on the tailing 0.08 pounds per ton of additional lignin sulpho pond material using a synthetic hard water con ' nate in each step gave a ?nal concentrate which taining the equivalent of 13 grains of lime and 7 assayed 98.5 percent CaFz, 1.1 percent CaCOs, and 0.3 percent S102, and represented a recovery 35 grains of magnesia per gallon. A typical test using the hard water in the grinding, roughing, of 83.4 percent of the total ?uorspar. . ' and cleaning operations gave a 79.4 percent re A duplicate of the preceding test using a mag covery of the ?uorspar in concentrates which nesium lignin sulphonate gave an 84.2 percent assayed 98.3 percent CaFz, 0.5 percent CaCOa, recovery of acid grade spar concentrates. An other test using calcium lignin sulphonate gave 40 and 0.07 percent SiOs. The ground pulp was conditioned 5 minutes with 2.0 pounds per ton 77.1 percent recovery of ?uorspar in concen tratespf acid grade.' Considerable latitude was - of soda ash and 1.0 pound per ton, respectively, of sodium ?uoride and magnesium lignin sul apparent in the ?otation testing of the tailing phonate. Oleic acid equivalent to 0.64 pound per pond material both in the choice} of the lignin sulphonate ‘for retardation of the gangue, and 45 ton was added as the ?uorspar collector and the trates of acid grade.‘ permissible. - ~ - . " ration. - in the relative proportions of collector, sodium ?uoride, and lignin sulphonate employed. ' ' > pulp conditioned for an additional 5 minutes. Flotation of the ?uorspar in the roughing opera tion proceeded in a normal fashion and was com Comparative ?otation tests using sodium or plete in 3 minutes. The rougher froth was re ammonium ?uoride as the addition agents in conjunction with the various lignin sulphonates 50 pulped with additional hard water and re?oated twice using 0.5 and 0.2 pounds per ton of the _ gave substantially identical results. Aluminum magnesium lignin sulphonate in the ?rst and ?uoride and sodium silico-?uoride were also second cleaner. A third and ?nal ‘cleaning oper satisfactory vbut were less effective than the ation using hard water but without ~additional sodium or ammonium ' salts because of their lower ‘solubility. Various other addition agents 55 lignin sulphonate yielded acid grade ?uorspar concentrates of the grade and recovery given including sodium sul?de, sodium sul?te, sodium above. Combinations of soda'ash and caustic meta- and per-borate, ammonium and‘ sodium soda or soda ash and sodium silicate were used acetate, potassium'ferro and ferri cyanide, so in other. tests to pre-condition the hard water dium ortho, pyro, and metaphosphate, soda ash, sodium silicate, and caustic soda were used in 60 pulp before ?otation of the ?uorspar by the prac tice previously described. Good ?otation of the conjunction with the lignin sulphonates in other ?uorspar was achieved by the various modi?ca ?otation tests on the tailing pond material. tions provided the pH of the pulp did not exceed These reagents were somewhat less eifective than 11, and preferably was less than 10. the ?uorides but enabled an improved separation of the ?uorspar. 65 Example 111 I Sodium sul?de was particularly advantageous The examples of practice described heretofore and a typical test using this reagent in conjunc demonstrate the applicability of this invention tion with magnesium lignin sulphonate gave an 81.0 per cent recovery of ?uorspar in concen to the recovery of ?uorspar from ores contain-.' dure employed in the test was as follows: The ground charge was conditioned 15 minutes with 2.0 pounds per ton of a crude sodium sul?de practice on an ore ‘containing a substantial trates which assayed 98.4 percent CaF2, 0.9 per 70 ing siliceous or calcareous gangue constituents. We shall now describe the results obtained by its cent CaCOa, and 0.1 percent $102. The proce amount of barite together with calcite and quartz. The sample was from a Canadian deposit product commonly known as “GO-percent Fused 75 and assayed 53.5 percent CaFh, 7.0 percent 1 13 2,407,661 08.003, 0.6 percent S102, and‘ 37.1 percent BaSOu. Grinding to 65 mesh gave adequate liberation of the ?uorspar for the production of acid grade concentrates by this invention. A representative portion of the Canadian sam ple was ground to 65 mesh and froth ?oated by 14 and 0.64 pound oi.’ oleic acid as the collector gave a 67.9 percent recovery of the ?uorspar in concen trates which assayed 98.4 percent CaFz, 0.6 per; cent CaCOa, 0.10 percent B84304, and 0.14 per cent SiOz. These results are about average of the procedure described in Example I using 2.0 pounds per ton of sodium ?uoride, 5.0 pounds per those obtained with various lignin sulphonates without sodium ?uoride or other addition agents. 0.13 percent SiO2, and 0.05 percent BaSO4, and. to?uorspar ores containing variable quantities Numerous ?otation tests have been made on a ton of an evaporated crude sul?te waste liquor of ?uorspar ores containing from :none to containing about 50 percent of magnesium base 10 variety as much as 70 percent barite using the combina llignin sulphonic acids, and 0.32 pound per ton tion of sodium ?uoride and lignin sulphonates to of crude oleic acid as the collecting agent. retard the barite. All of the ores responded‘r Roughing and triple-cleaning of the froth prod readily to our method of ?otation and yielded uct yielded a ?nal ?uorspar concentrate which acid grade ?uorspar concentrates essentially free assayed 99.2 percent CaFa, 0.4 percent CaCOa, 15 of barite. Our method of ?otation is applicable represented a recovery of 87.1 percent of the ?uor of barite for the recovery of- high grade ?uor spar in the ?otation feed. About 90 percent of spar concentrates; conversely, the method may be the silica and 99 percent of the barite and calcite used for the puri?cation of barite ores contain were rejected in the roughing and cleaning treat 20 ing ?uorspar as a contaminant. ment. Various of the commercially available liquid Example IV and dehydrated residues from crude and puri?ed sul?te liquors were used in conjunction with sodium ?uoride in other tests on the Canadian 25 material for retardation of the gangue while ?oating the ?uorspar with fatty acid or soap col lectors. The relative proportion of the lignin sulphonates, sodium ?uoride, and collector was subject to considerable variation and the proper quantities had to be determined by trial. Mod erate variation in the quantities of the lignin sulphonate and sodium ?uoride was permissible and did not seriously impair selectivity of the separation. The crude and puri?ed lignin sul 35 phonates were used interchangeably in ?otation with uniformly good results. The crude products were slightly less effective than the puri?ed sul phonates for retarding barite but were particu larly attractive due to their lower cost. 40 Another test on the Canadian sample using 2.0 pounds per ton sodium ?uoride and 1.0 pound per ton of substantially pure magnesium lignin sulphonate residue gave an 86.7 percent recovery of ?uorspar in acid grade concentrates contain 45 ing 0.15 percent BaSO4. Similar tests using 2.0 A ?uorspar ore from a, Kentucky deposit con and 5.0 pounds per ton of the magnesium sul phonate yielded recoveries of 89.4 and 95.3 per cent of the ?uorspar in concentrates containing less than 0.1 percent barite. ‘Another series of 50 tests using 0.5, 1.0, 2.0, and 5.0 pounds per ton of sodium ?uoride, respectively, in conjunction taining barite, celestite, calcite, and quartz to gether with minor amounts of galena and sphal erite as the gangue materials was next exam ined. A head analysis gave 34.5 percent CaFz, 5.9 percent CaCos, 46.7 percent BaSOr, 7.5 per cent SrSO4, 3.6 percent SiOz, 0.2 percent Pb, and 0.5 percent Zn. The ?ourspar was intimately as sociated with the gangue and grinding ‘to 150 mesh was required for liberation. A representative portion of the ore was ground to 150 mesh and froth ?oated by the procedure described in Example I using 2.0 pounds per ton of sodium ?uoride and magnesium lignin sul phonate as the depressants and 0.32 pound per ton of commercial oleic acid as the ?uorspar col lector. The rougher froth was triple-cleaned with 0.08 pound per ton of the lignin sulphonate in each step and yielded a ?nal ?uorspar concen trate which assayed 98.8 percent CaFz, 0.8 per cent 02.003, 0.07 percent BaSO‘i, 0.10 percent SrSO4, 0.2 percent SiOz, and only a trace of lead or zinc. The ?uorspar recovery in the test was 78.3 percent. An excellent rejection of barite, celestite, calcite, silica, and metallic sul?des was eiTected by the combination of sodium ?uoride and the lignin sulphonate. Example V‘ A ?uorspar ore containing substantial amounts with 2.0 pounds per ton of the lignin sulphonate of galena (PbS) and sphalerite (ZnS) in addition and 0.32 pound per ton of oleic acid as the col to calcite and silicawas obtained from the Cave lector gave recoveries of 47.9, 89.2, 89.4, and 79.6 55 in Rock area of the Southern Illinois ?uorspar percent of the ?uorspar in acid grade concen district. A head analysis gave 51.4 percent CaFz, trates containing less than 0.1 percent barite. 10.9 percent CaCOz, 15.5 percent S102, 3.5 per Calcium and sodium lignin sulphonates in con cent Pb, and 10.5 percent Zn. junction with sodium ?uoride gave results en A portion of the ore was ground to 100 mesh tirely similar to those obtained by the magnesium 60 and froth ?oated by customary sul?de ?otation compound. These tests demonstrate that the methods to recover the galena and sphalerite. combination of sodium ?uoride and a lignin sul The sul?de tailing containing 0.2 percent Pb, phonate is very effective for the retardation of 0.7 percent Zn, and 68.1 percent CaFz was re barite in ?uorspar ?otation. The separation is treated by this invention to recover the ?uorspar highly speci?c and considerable latitude is ap 65 in acid grade concentrates. The tailing from’ parent both in the choice of the lignin sulphonate sul?de ?otationwas conditioned 5 minutes with and in the relative proportions of sulphonate and 2.0 pounds per ton of sodium ?uoride and magne ?uoride employed. sium lignin sulphonate, respectively, and 0.32 Although the combination of sodium ?uoride pound per ton of oleic acid was then added and and lignin sulphonate is particularly effective for 70 the pulp conditioned an additional 5 minutes. retarding barite in ?uorspar ?otation, the lignin Air was admitted to the cell and the rougher froth sulphonates may be used alone with good results. A typical test on the Canadian sample employing the procedure described in Example I using 2.0 collected for 3 minutes when ?otation of the ?uorspar was completed. The froth product assayed 86.1 percent CaFz and contained 97.0 pounds per ton of magnesium lignin sulphonate 75 percent of the ?uorspar in the original sample. 2,407,651 15 The tailings assayed 5.8 percent CaFz and ac counted for a loss of 1.9 percent of the total ?uorspar. The ?uorspar rougher froth was re sample. 16 Triple-cleaning of the rougher froth using 0.08 pound per ton’ of additional calcium lignin sulphonate in each vstep yielded a ?nal ?uorspar concentrate which assayed 97.7 percent . pulped with tap water and re?oated using 0.08 CaFz, 1.5 percent CaCOa, and 0.5 percent SiOz, pound per ton of the lignin sulphonate to retard and represented a recovery of 89.1 percent of the the gangue. Three such cleaning steps yielded total ?uorspar. A cumulative sizing analysis of a ?nal ?uorspar concentrate which assayed 98.2 the ?uorspar concentrates showed that 22.8 per percent CaF2, 0.6 percent CaCOz, 0.3 percent SiOz. cent of the ?uorspar was coarser than 28 mesh. 0.05 percent Pb, and 0.06 percent Zn, and repre sented a recovery of 95.0 percent of the total 10. 45.0 percent was coarser than 35 mesh, and 60.1 percent was coarser than 48 mesh. ‘ ?uorspar in the original material. While we have disclosed the presently preferred The reagent used in the test for ?otation of embodiment of our invention, it will be readily the galena and sphalerite included copper sulfate, apparent to those skilled in the art that many potassium ethyl and amyl xanthates, phospho variations and modi?cations may be made therein cresylic acid, and pine oil. These reagents ex without departing from the spirit and scope of hibited no deleterious effect in the subsequent the invention as de?ned in the appended claims. ?otation of ?uorspar by this invention. The What is claimed is: combination of sodium ?uoride and lignin sul 1. The process of concentrating ?uorspar by phonate adequately retarded the metallic sul?des remaining in the ?uorspar feed as well as the cal 20 froth ?otation of pulps containing ?uorspar values, comprising adding to such a pulp sodium careous and siliceous gangue materials. Sodium cyanide was used in other tests on the Cave in Rock sample to complex or precipitate ?uoride, a lignin sulphonate, and a ?uorspar col lecting agent selected from the class consisting of fatty acids and soaps, and subjecting said pulp sul?de tailings prior to ?otation of the ?uorspar 25 to froth ?otation to recover the ?uorspar. 2. The-process of concentrating ?uorspar by by our method. The combination of sodium cy froth ?otation of pulps containing ?uorspar anide and ?uoride was particularly advantageous values, comprising adding to such a pulp a soluble for overcoming the deleterious effect of metal inorganic ?uoride, a lignin sulphonate, and a salts in ?uorspar/?otation. Cyanide and ?uoride complement each other and the proper propor 30 ?uorspar collecting agent selected from‘ the class consisting of fatty acids and soaps, and subject tions for optimum retardation of the gangue by ing said pulp to froth ?otation to recover the the lignin sulphonates may best be determined the metal salts (i. e.‘ copper and zinc sulfate) in ?uorspar. 3. The process of concentrating ?uorspar by Various of the commercially available liquid and dehydrated residues of sul?te liquors have 35 froth ?otation of pulps containing ?uorspar val by experimentation. been successfully used in conjunction with sodium ?uoride and sodium cyanide, singly or together, for the retardation of metallic sul?des and cal ues, comprising adding to such a pulp a pH mod ifying agent to establish a pH not to exceed 11, a soluble inorganic ?uoride, a lignin sulphonate, and a ?uorspar collecting agent selected from the careous and siliceous gangue materials in ?uor spar ?otation of sul?de tailings. No difficulty has 40 class consisting of fatty acids and soaps, and subjecting said pulp to froth ?otation to recover been experienced in obtaining'a satisfactory re the ?uorspar. covery of acid grade ?uorspar concentrates essen 4. The process of concentrating ?uorspar by tially free of metallic sul?des. froth ?otation of pulps containing ?uorspar val Example VI ues, comprising adding to the pulp sodium sul ?de, a pH modifying agent to establish a pH not ‘We have discovered that our method of ?ota to exceed 11, a lignin sulphonate, and a ?uorspar tion enables the recovery of coarser ?uorspar than collecting agent selected from the class consist~ was formerly believed, possible by older methods ing of fatty acids and soaps, and subjecting said of ?otation. Fluorspar as coarse as 20 mesh has been satisfactorily separated from calcareous and 50 pulp to froth ?otation to recover the ?uorspar. 5. The process of concentrating ?uorspar by siliceous gangue constituents by the practice of froth ?otation of pulps containing ?uorspar val this invention and it seems likely that even coarser ues, comprising adding to the pulp a lignin sul material may be made to yield to our method phonate, sodium cyanide and an inorganic sol of ?otation. An illustrative example of the prac tice of this invention for the recovery of coarse 55 uble ?uoride, and a ?uorspar collecting agent comprising oleic acid, and subjecting said pulp to ?uorspar will not be given. ' froth ?otation to recover the ?uorspar. A jig tailing from an operating plant in the 6. The process of concentrating ?uorspar by Southern Illinois ?uorspar district was obtained froth ?otation of pulps containing ?uorspar val for testing. The material as received was essen tially ?ner than 6 mesh and assayed 44.6 percent 60 ues, comprising adding to the pulp a metal salt of lignin sulphonic acid, an inorganic soluble CaFz, 42.1 percent CaCOa, and 12.1 percent S102. ?uoride,‘ and a ?uorspar collecting agent selected A representative portion of the sample was care from the class consisting of fatty acids and soaps, fully ground to pass 20 mesh and froth ?oated and subjecting said pulp to froth ?otation to re to recover the ?uorspar by the procedure described in Example I. Sodium ?uoride, calcium lignin 65 cover the ?uorspar. '7. The process of concentrating ?uorspar by sulphonate, and oleic acid were used in the rough froth ?otation of pulps containing ?uorspar val— ing operation in amount equivalent to 2.0, 2.0. and ues, comprising adding to the pulp a substantially 0.64 pounds per ton respectively. The rougher dehydrated residue of paper mill'sul?te liquors, froth, collected for 2.5 minutes, assayed 84.6 per cent CaFz, 13.3 percent CaCOa, and 1.6 percent 70 an inorganic soluble ?uoride, and a ?uorspar collecting agent selected from the class consist ‘SiOz, and represented a recovery of 94.2 percent ing of fatty acids and soaps, and subjecting said of the ?uorspar. The ?otation tailings assayed pulp to froth ?otation to recover the ?uorspar. 5.1 percent CaFz, 70.5 percent 021003, and 22.4 8. The process of concentrating ?uorspar by percent Si02, and contained 84.3 percent of the calcite and 93.4 percent of the silica in the original 75 froth ?otation of pulps containing ?uorspar val 17 2,407,651 ues, comprising adding to the pulpa paper mill sul?te liquor, an inorganic soluble ?uoride, and a ?uorspar collecting agent selected from the class consisting of fatty acids and soaps, and subjecting ’ said pulp to froth ?otation to recover the ?uor spar. 9. The process .of concentrating ?uorspar by froth ‘?otation of pulps containing ?uorspar val ues, comprising adding to the pulp a lignin sul 18 froth ?otation of deslimed pulps containing ?uor spar values, comprising adding to the substan tially deslimed pulp a paper mill ligneous sub stance selected from the class consisting of sul ?te liquor and dehydrated residues thereof, an inorganic soluble ?uoride, and a ?uorspar collec tor selected from the class consisting of fatty acids and soaps, and subjecting said pulp to froth ?otation to recover the ?uorspar. _ phonate, a tannin extract and a ?uorspar collect 10 13. In a process for the bene?ciation of a ing agent selected from the class‘ consisting of ?uorspar ore involving the froth ?otation of an fatty acids and soaps, and subjecting said pulp aqueous pulp of such an ore in the presence of a to froth ?otation in the presence of a soluble fatty acid collector and the recovery in the froth substance yielding ?uoride ions in solution, to of a ?uorspar concentrate, the step which, com recover the ?uorspar. 15 prises carrying out the ?otation in the presence of 10. The process of concentrating ?uorspar by a soluble substance yielding ?uoride ions in solu froth ?otation of pulps containing ?uorspar val tion, a substance adapted to depress barite in the ues, comprising adding to the pulp a tannin ex presence of a soluble ?uoride comprising a lignin tract, a paper mill ligneous substance selected from the class consisting of sul?te liquor and de 20 sulphonate. and a substance adapted to depress calcite comprising a tannin extract, whereby the hydrated residues thereof, an inorganic soluble normal propensity of a tannin extract to ?oat ?uoride, and a ?uorspar collecting agent selected barite is inhibited by said ?uoride. from the class consisting of fatty acids and soaps, 14. The process of claim 13, wherein tall oil and subjecting said pulp to froth ?otation to is employed as the collector. recover the ?uorspar. 25 15. The process of claim 13, wherein sodium 11. The process of concentrating ?uorspar by ?uoride is employed as the soluble ?uoride. froth ?otation of deslimed pulps containing ?uor 16. The process of claim 13, wherein a lignin spar values, comprising adding to the substan sulphonate derived from paper mill sul?te liquor tially deslimed pulp a paper mill ligneous sub is employed. stance selected from the class consisting of sul The process of claim 13, wherein quebracho ?te liquor and dehydrated residues thereof, a 30 is 17. employed as the tamiin extract. ?uorspar collecting agent selected from the class 18. The process of claim 13, accompanied by consisting of fatty acids and soaps, and sub i an additional treatment to diminish the pulp con jecting said pulp to froth ?otation in the pres centration of soluble polyvalent cations. - ence of a soluble substance yielding ?uoride ions 35 in solution, to recover the ?uorspar. 12. The process of concentrating ?uorspar by JULIUS BRUCE CLEMMER. BALLARD H. CLEM'MOI-NS.