Bureau of Mines

Report of Investigations 5312

4

BENEFICIATION OF IRON-COPPER ORES

FROM KASAAN PENINSULA,

PRINCE OF WALES ISLAND, ALASKA

BY R. R. WELLS, E. G. ERSPAMER, AND F. T. STERLING

- United States Department of the Interior--February 1957

-
I

BENEFICIATION OF IRON-COPPER ORES

FROM KASAAN PENINSULA,

PRINCE OF WALES ISLAND, ALASKA

BY R. R. WELLS, E. G. ERSPAMER, AND F. T. STERLING

* * * * * * * * Report of Investigations 5312

UNITED STATES DEPARTMENT OF THE INTERIOR

Fred A. Seaton, Secretary

BUREAU OF MINES

Marling J. Ankeny, Director

Work on manuscript completed August 1956. The Bureau of Mines will welcome reprinting of this paper, provided

the following footnote acknowledgment is made: "Reprinted from Bureau of Mines Reportof Investigations5312."

February 1957
BENEFICIATION OF IRON-COPPER ORES FROM KASAAN PENINSULA,

PRINCE OF WALES ISLAND, ALASKA

by

R. R. Wells,- / E. G. Erspamer, 2/ and F. T. Sterling2/

CONTENTS

Page

Summary ....................................................... 1

Introduction ......................................... .......... 2

The ore ...................................................... 2

Samples ................................... , .......... 2

Physical character ...................................... ... 5

Poorman ore ...................................... ... 5

Rush & Brown ore .................................... 5

Copper Center ore .....................................

Chemical character ........................................ 5

Methods of concentration ....................................... 6

Direct wet magnetic separation ............................ 7

Two-stage magnetic separation ............................. 9

Magnetic separation followed by flotation ................ 10

Flotation followed by magnetic separation .................. 12

Sintering ................................................ 14

Flowsheet ............................................ .... 14

/ Supervising metallurgist, Bureau of Mines, Region I, Juneau

Alaska.

2/ Formerly metallurgist, Bureau of Mines, Region I, Juneau, Alaska.

3/ Extractive metallurgist, Bureau of Mines, Region I, Juneau, Alaska.

Report of Investigations 5312
ii

Fig. Page

1. Index map of southeastern Alaska ......................... 3

2. Vicinity map, Kasaan Peninsula ........................... 4

3. Suggested flowsheet ...................................... 15

TABLES

1. Summary of results ........................................ 1

2. Chemical analyses ....................................... 6

3. Spectrographic analyses ............................. 6....

4. Wet magnetic separation, Poorman ......................... 7

5. Wet magnetic separation, Rush & Brown .................... 8

6. Wet magnetic separation, Copper Center ................... 9

7. Two-stage magnetic separation, Poorman ................... 10

8. Magnetic separation followed by flotation, Poorman ....... 10

9. Magnetic separation and flotation, Rush & Brown ........... 11

10. Magnetic separation and flotation, Copper Center ......... 11

11. Flotation followed by magnetic separation, Poorman ....... 12

12. Flotation and magnetic separation, Rush & Brown .......... 12

13. Flotation and magnetic separation, Copper Center .......... 13

14. Sintering results ........................................ 14
1

SUMMARY

This report summarizes the results of laboratory testing of copper-bearing

magnetite ore from the Poorman, Rush & Brown, and Copper Center deposits, Kasaan

Peninsula, Prince of Wales Island, southeastern Alaska. The ores contain minor

amounts of chalcopyrite and pyrite. Intimate association of these sulfides with

magnetite necessitates fine grinding for adequate liberation and rejection of copper

and sulfur and for the production of high-grade iron concentrate low in objectionable impurities.

Laboratory tests indicated that the optimum results can be obtained by flotation of ore ground to minus-100-mesh, with subsequent wet magnetic separation treatment of the flotation tailing. A summary of results obtained by this treatment of

the three samples tested is shown in table 1.

TABLE 1. - Summary of results

Copper concentrate

Iron concentrate Grade

Head Grade Distb., Assay, Distb.,

Assay, percent Assa prcent percent percent percent

Ore Fe Cu S F Cu S Fe Cu Cu

Poorman ...... 55.2 0.32 3.86 6. 0.03 0.03 88. 25.1 69.3

Rush & Brown.. 54.6 1.10 2.32 68.2 .10 .9 88.9 24.6 70.6

Copper Center. 50.6 1.85 3.73 0.3 . .06 86.8 19.3 87.2

The three ores were amenable to flotation and magnetic separation treatment for

the production of high-grade magnetite concentrate of low copper content. The method

was effective for virtually complete removal of sulfur from the Poorman and Copper

Center ores. The concentrate made from Rush & Brown ore contained 0.9 percent S;

subsequent sintering, however, reduced the sulfur content to 0.15 percent. Total

iron recovery ranged from 87 to 89 percent; this represents a recovery of approximately 99 percent of the magnetite present.

Cleaning of the flotation concentrates yielded copper products that assayed 19

to 25 percent Cu. Copper recovery ranged from 69 to 87 percent, depending upon the

copper content of the various samples.

A similar method is in actual commercial use in eastern Pennsylvania, where

ore from the Cornwall mine is crushed, concentrated and sintered profitably by the

Bethlehem Steel Corp.
2

INTRODUCTION

Early in the century numerous deposits of copper ore were discovered on Kasaan

Peninsula, Prince of Wales Island, Alaska (fig. 1); a smelting plant was built at

Hadley, and shipments of ore were made from several mines. Deposits of magnetite

were found to be associated closely with the copper ores but were not exploited.

In 1915 Wright4/ reported:

The only iron ore found in Kasaan Peninsula and the Copper Mountain

area is magnetite which occurs in large bodies along contacts of diorites

and limestones. No special study has been made of these deposits, which

have been developed only in connection with the mining of the copper ores....

The utilization of these iron ores would seem to be a metallurgical problem,

as there is no question that they occur in quantities that should make them

commercially valuable.

In 1942 to 1944 the Bureau of Mines examined the more promising magnetite bodies by trenching, diamond drilling, and sampling.5 6 7 8 9/ Preliminary mineraldressing studies were conducted on Poorman ore and on Mount Andrew ore. It was

determined that the ores are similar; they consist of irregular contact metamorphic

deposits of magnetite and quartz with minor amounts of chalcopyrite and pyrite.

Because copper and sulfur are detrimental in iron and steel processing, the ores

would require beneficiation treatment to fit them for blast-furnace use.

Although the known reserves of individual deposits are relatively small, the

combined reserves within a limited area have been indicated to be substantial;

therefore the purpose of this laboratory investigation was to develop a simple

method of concentration that would be applicable to each of the deposits.

THE ORE

Samples

During a field investigation in the Kasaan Peninsula area (fig. 2), samples

for metallurgical testing were obtained from the Poorman, Rush & Brown, and Copper

4/ Wright, Charles Will, Geology and Ore Deposits of Copper Mountain and Kasaan

Peninsula, Alaska: Geol. Survey Prof. Paper 87, 1915, 110 pp.

5/ Wright, W. S., and Posse, E. L., Exploration of the Jumbo Basin Iron Deposit,

Prince of Wales Island, Southeastern Alaska: Bureau of Mines Bept. of Investigations 3952, 1946, 9 pp.

6/ Wright, W. S., and Tolonen, A. W., Mount Andrew Iron Deposit, Kasaan Peninsula,

Prince of Wales Island, Southeastern Alaska: Bureau of Mines Rept. of

Investigations 4129, 1947, 27 pp.

7/ Holt, S. P., and Sanford, Robert S., Poor Man Iron Deposit, Kasaan Peninsula,

Prince of Wales Island, Southeastern Alaska: Bureau of Mines Report of

Investigations 3956, 1946, 8 pp.

8/ Holt, S. P., Shepard, J. G., Thorne, R. L., Tolonen, A. W., and Fosse, E. L.,

Diamond Drilling at Rush & Brown Copper Mine, Kasaan Bay, Prince of Wales

Island, Southeastern Alaska: Bureau of Mines Rept. of Investigations 4349,

1948, 7 pp.

9/ Erickson, Aner W., Investigation of Tolstoi Mountain Iron Deposits, Kasaan

Peninsula, Prince of Wales Island, Southeastern Alaska: Bureau of Mines

Rept. of Investigations 4373, 1948, 5 pp.
Figure 1. - Index map of southeastern Alaska. (Modified from mop of Geological Survey.) UJ
Figure 2. - Vicinity map, Kasaan Peninsula.
5

Center properties. A suite of samples was taken from old adits and trenches at the

Poorman mine; the individual samples were assayed and blended to produce a composite

which, as nearly as possible, was representative of the ore body as determined by

previous field work.l1/ The samples from the Rush & Brown and the Copper Center

properties were, of necessity, procured from ore dumps near the portals of these

mines. Consequently, the chemical analyses of these samples may be at variance with

the average grade of the deposits. The samples tested, however, are believed to be

representative of the ore of the Rush and Brown and the Copper Center mines in regard

to physical and mineralogical nature.

Physical Character

Poorman Ore

The Poorman ore, as represented by the composite sample, contains magnetite

with relatively small amounts of associated pyrite, chalcopyrite, calcite, altered

amphibole and clinopyroxene, chlorite, quartz, altered feldspar, epidote, and

limonite. Traces of malachite and apatite are also present.

The magnetite essentially is liberated in the minus-100-, plus-200-mesh fraction; however, a small amount of the fine-grained material remains locked with calcite and ferromagnesian minerals in the minus-200-mesh material. The chalcopyrite

essentially is liberated in the minus-35-, plus-48-mesh size range.

Rush & Brown Ore

The sample of Rush & Brown ore submitted to the laboratory essentially contains

magnetite, with some associated calcite, quartz, chalcopyrite, pyrite, chlorite,

pyrrhotite, and limonite and small amounts of malachite and azurite.

Much of the chalcopyrite and malachite is liberated in the plus-200-mesh fraction. Because of the intimate association of the copper minerals with the other

minerals of this sample, however, complete liberation does not take place, even in

the minus-200-mesh.

Copper Center Ore

The sample of Copper Center ore essentially contains magnetite, with some associated quartz, chlorite, chalcopyrite, epidote, limonite, and small amounts of

calcite, pyrite, malachite, amphibole, and azurite.

Much of the chalcopyrite, malachite, and azurite is liberated in the plus-200-

mesh fraction. Complete liberation is not effected, however, even in the minus-200-

mesh size range, because of intimate association of the copper minerals with magnetite and quartz.

Chemical Character

Chemical analyses of representative portions of the ores are shown in table 2.

l0/ Work cited in footnote 7 (p. 2).
6

TABLE 2. - Chemical analyses

Assa, percent Oz. per ton

Ore Fe Cu S P CaO MgO Si02 Au Ag

Poorman ..... 55.2 0.32 3.8 0.03 3.2 1.3 9.7 0.02 0.03

Rush & Brown. 54.6 1.10 2.32 _J.O1 4.0 .9 6.6 .01 Tr.

Copper Center 50.6 1.85 3.73 1/.01 2.6 .9 13.4 .05 .25

1/ Less than.

Semiquantitative spectrographic analyses indicated the presence and approximate

amounts of the metals shown in table 3. Any other elements, if present, are in

amounts less than the minimum detectable by the routine method used.

TABLE 3. - Spectrographic analyses

Ore Al As C Co Fe MnMoNa Ni Si Ti B

Poorman ......... D- - E - D- A F E - - F D E F

Rush & Brown ...... C - C F C A C D E- - F A E -

Copper Center ..... C D C - C A C- D - D F A E

Legend: A More than 10 percent. D 0.1 to 1 percent.

B 5 to 10 percent. E 0.01 to 0.1 percent.

C 1 to 5 percent. F 0.001 to 0.01 percent.

METHODS OF CONCENTRATION

Iron ore is a relatively low-priced commodity. Mineral-dressing treatment,

therefore must be simple and inexpensive if the beneficiated product is to compete

with direct-smelting ores. In addition, the beneficiated product must be made to

conform to chemical and physical requirements for blast-furnace feed.

Inasmuch as smelting costs rise rapidly with the amount of slag-forming constituents in the ore, the ideal blast-furnace feed should be as high in iron and as

low in silica content as possible. Both sulfur and phosphorus are deleterious,

hence only minor amounts of these impurities are allowable. The presence of copper

in significant quantities is considered undesirable. The physical condition of the

feed is as important as its chemical composition. The product should be free of

lumps greater than 6 inches in diameter and also should be free of fine material.

Fine concentrate, therefore, requires sintering or nodulizing to meet physical

specifications.

During this investigation, laboratory testing was directed toward production

of a concentrate that contained at least 65 percent Fe, with a maximum of 0.10 percent each Cu and S. None of the ores tested contained appreciable amounts of phosphorus; consequently elimination of this element imposed no problem.

Because of the fine-grained nature of the ores, concentration testing was restricted to wet magnetic separation and flotation methods. Preliminary sintering

tests were made on beneficiated products to determine the effectiveness of sintering for elimination of sulfur.
7

Direct Wet Magnetic Separation

To determine the degree of grinding necessary to effect rejection of copper

and sulfur, samples of Poorman ore were ground to pass various screens ranging from

10- to 325-mesh. Each ground portion was treated in a low-intensity wet magnetic

separator (Davis-tube type) to produce magnetic and nonmagnetic fractions. Similar

treatment was given samples of Rush & Brown and Copper Center ores at sizes ranging

from minus-20-mesh to minus-325-mesh. Results, showing iron, copper, silica, and

sulfur contents, together with the distribution of these elements in each fraction,

are summarized in tables 4, 5, and 6.

TABLE 4. - Wet magnetic separation, Poorman

Grind Weight sAssay,percent Distribution, percent

(mesh) Product percent Fe Cu SiO2 S Fe Cu SiO2 S

Minus-10 Magnetic l81.91 63.5 0.18 5.80 1.10 93.2 41.6 51.1 244

Nonmag. 18.09 21.1 1.14 25.1 15.5 6.8 58.4 48.9 17.6

Calc. head 100.00 55.8 .35 9.3 3.70 100.0 100.0 00 .0 100.0

Minus-20 Magnetic 78.35 63.9 .14 5.72 1.04 93.0 30.9 48.8 21.2

Nonmag. 21.65 17.5 1.12 21.7 14.0 7.0 69.1 51.2 78.8

Calc. head 100.00 53.9 .35 9.2 3.85 100.0 100.0 100.0 100.0

Minus-35 Magnetic 76.87 64.8 .12 5.68 .68 92.1 27.4 45.0 14.8

Nonmag. 23.13 18.5 1.10 23.1 13.0 7.9 72.6 55.0 85.2

Calc. head 100.00 54.1 .35 9.7 3.53 100.0 100.0 100.0 100.0

Minus-48 Magnetic 75.86 65.6 .11 5.08 .51 91.3 23.5 40.9 11.0

Nonmag. 24.14 19.7 1.12 23.1 13.0 8.7 76.5 59.1 89.0

Calc. head 100.00 54.5 .35 9.4 3.52 100.0 100.0 100.0 100.0

Minus-65 Magnetic 74.91 67.2 .09 4.62 .25 91.0 19.3 38.0 5.1

Nonmag. 25.09 19.8 1.12 22.5 13.9 9.0 80.7 62.0 94.9

Calc. head 100.00 55.3 .35 9.1 3.68 100.0 100.0 100.0

Minus-100 Magnetic 73.32 67.2 .09 4.30 .05 91.0 18.8 32.5 1.1

Nonmag. 26.68 18.3 1.07 24.6 12.0 9.0 81.2 67. _98.9

Calc. head 100.00 54.2 .35 9.7 3.24 100.0 100.0 100.0 100.0

Minus-150 Magnetic 73.28 68.6 .07 3.80 .04 90.6 14.7 30.7 0.8

Nonmag. 26.72 19.6 1.11 23.5 13.1 9.4 85.3 69.3 99.2

Calc. head 100.00 55.5 .35 9.1 3.53 100.0 100. 1.0 100.000.0

Minus-200 Magnetic 73.19 68.6 .04 3.48 .02 90.3 8.2 28.7 .5

Nonmag. 26.81 20.6 1.21 23.6 13.0 Q9.7 91.8 71.3 99.5

Calc. head 100.00 55.6 .35 8.9 3.50 100.0 100.0 100.0 100.0

Minus-325 Magnetic 73.03 69.0 .03 3.24 1/.01 89.6 6.5 25.2 .1

Nonmag. 26.97 21.6 1.18 26.0 14.3 10.4 93.5- 74.8 99-9

C__alc. head 100.00 -1 .2 .34 9.4 3.86 10 100.0 1000.0 100.0

l/ Less than.
8

TABLE 5. - Wet magnetic separation, Rush & Brown

Grind Weight, Assay, ercent Distribution, percent

(mesh) Product percent Fe Cu Si02 S Fe Cu Si02 S

Minus-20 Magnetic 84.23 63.0 0.26 T4. 1.2 93.9 22.1 58.9 40.8

Nonmag. 15.77 21.7 4.9 17.5 9.3 6.1 77.9 41.1 59.2

Calc. head 100.00 56.5 1.00 6.7 2.48 .O 100.0 100.0 100.0000 00

Minus-35 Magnetic 82.21 64.0 .20 3.7 1.1 93.5 17.0 46.6 37.7

Nonmag. 17.79 20.6 4.5 19.7 8.4 6.5 83.0 53.4 62.3

Calc. head 100.00 56.3 .95 6.5 2.40 100.0 100.0 100.0 100.0

Minus-48 Magnetic 79.54 64.6 .14 3.3 .90 92.3 11.7 39.8 30.4

Nonmag. 20.46 21.0 4.1 19.4 8.0 7.Z 88.3 60.2 69.6

Calc. head 100.0 55.7 .95 6.6 2.35 100.0 100.0 100.0 100.0

Minus-65 Magnetic 78.92 66.2 .10 3.0 .88 92.2 8.4 35.5 30.0

Nonmag. 21.08 21.2 4.3 20.4 7.7 7.8 91.6 64.5 70.0

Calc. head 100.00 56.7 .95 6.7 2.32 100.0 100.0 100.0 100.0

Minus-100 Magnetic 78.65 66.3 .08 2.9 .85 91.7 6.6 34.3 29.2

Nonmag. 21.35 22.0 4.2 20.5 7.6 8.3 93.4 65.7 70.8

Calc. head 100.00 56.8 .95 6.7 2.29 100.0 100.0 100.0 100.0

Minus -150 Magnetic 78.62 66.4 .08 2.4 .82 91.7 6.6 29.5 27.6

Nonmag. 21.38 22.1 4.2 21.1 7.9 8.3 93.4 70.5 72.4

Calc. head 100.00 56.9 .95 6.4 2.33 100.0 100.0 100.0 100.0

Minus-200 Magnetic 76.41 67.4 .08 2.3 .80 90.5 6.5 26.1 27.0

Nonmag. 23.59 22.8 3.7 21.1 7.0 9.5 935 73.9 73.0

Calc. head 100.00 56.9 .95 6.7 2.26 100.0 100.0 100.0 100.0

Minus-325 Magnetic 75.71 67.4 .06 2.2 .78 90.2 4.5 24.4 25.5

Nonmag. 24.29 22.8 3.9 21.2 7.1 9.8 95.5 75.6 74.5

Calc. head 100.00 56.6 1.00 6.8 2.32 100.0 100.0 100.0 100.0
9

TABLE 6. - Wet magnetic separation, Copper Center

Grind Weight, Assay, percent Distribution, percent

(mesh) Product percent Fe Cu Si02 S Fe Cu Siop S

Minus-20 Magnetic 69.75 5.3 0.21 3.0 0.57 7.6 15.788 10.3

Nonmag. 30.25 19.3 5.9 34.5 11.4 1.4 21.4 4 84.3 897

Calc. head 100.00 51.4 1.95 12.5 3.85 100.0 100.0 100. 1. 0 

Minus-35 Magnetic 66.36 67.2 .18 2.3 .26 88.0 6.2 12.1 4.7

Nonmag. 33.64 18.0 5.3 33.0 10.5 12.0 93.8 87.9 95.3

Calc. head 100.00 50.6 1.90 12.6 3.71 100.0 100.0 100.0 100.0

Minus-48 Magnetic 65.95 67.7 .14 2.3 .18 87.6 5.0 11.7 3.2

Nonmag. 34.05 18.6 5.1 33.7 10.6 12.4 95.0 88.3 96.8

Calc. head 100.00 51.0 1.80 13.0 3.73 100.0 100.0 100.0 100.0

Minus-65 Magnetic 65.09 69.0 .14 2.2 .08 87.5 4.9 10.7 1.4

Nonmag. 34.91 18.3 5.05 34.4 10.5 12.5 95.1 89.3 98.6

Calc. head 100.00 51.3 1.85 13.4 3.72 100.0 100.0 100.0 100.0

Minus-100 Magnetic 63.92 69.2 .08 2.0 .06 87.3 2.8 9.6 1.0

Nonmag. 36.08 17.8 4.95 33.2 10.2 12.7 97.2 90.4 99.¢

Calc. head 100.00 50.7 1.85 13.3 3.72 100.0 100.0 100.0 100.0

Minus-150 Magnetic 63.43 70.8 .04 1.5 .06 87.2 1.4 7.1 1.0

Nonmag. 6.57 18.0 4.9 33.8 10.0 12.8 98.6 92.9 99.0

Calc. head 100.00 51.5 1.80 13.3 3.70 100.0 100.0 100.0 100.0

Minus-200 Magnetic 63.00 70.9 .03 1.5 .06 86.8 1.0 7.3 1.0

Nonmag. 37.00 18.4 5.0 32.3 9.9 13.2 99.0 92.7 99.0

Calc. head 100.00 51.5 1.85 12.9 3.70 100.0 100.0 100.0 100.0

Minus-325 Magnetic 62.79 71.5 .03 1.3 .06 86.7 1.0 6.1 1.0

Nonmag. 37.21 18.5 5.1 33.5 10.2 13.3 I 99.0 93.9- 99.0

Calc. head 100.00 51.8 1.90 13.3 _385 100.0 10. 100. 100 0 1 .0 

The results of these series of tests showed that the Poorman, Rush & Brown, and

Copper Center ores, as represented by the samples tested, are readily amenable to

concentration by wet magnetic separation at relatively coarse sizes for the production of magnetite concentrates assaying more than 60 percent Fe. Intimate association of sulfides with the magnetite, however, necessitated grinding to approximately

100-mesh for adequate rejection of copper. Rejection of sulfur below the 0.10-percent limit was accomplished by treating minus-100-mesh Poorman and Copper Center ore

samples. In the case of Rush & Brown ore, however, no test yielded low-sulfur concentrate; by treatment of ore ground to minus-325-mesh, sulfur content was reduced

to 0.78 percent.

Two-Stage Magnetic Separation

To determine if a portion of the gangue could be rejected at relatively coarse

size, a sample of Poorman ore was roll-crushed to minus-10-mesh and then treated in

a wet magnetic separator. The magnetic fraction was reground to minus-100-mesh and

retreated. Results are shown in table 7.
10

TABLE 7. - Two-stage magnetic separation, Poorman

Weight, Assay, percent Distribution, percent

Product percent Fe Cu S Fe Cu S

Minus-100-mesh mag.... 74.51 67.2 0.09 0.10 89.7 19.2 2.0

Minus-100-mesh nonmag. 7.40 25.9 1.03 11.1 3.5 21.8 22.2

Minus-10-mesh nonmag.. 18.09 21.1 1.14 15.5 6.8 5. 75 .8

Calc. head ........... 100.00 55.8 .35 3.70 100.0 100.0 100.0

Combined nonmag. .......... 4 22.5 1.11 14.2 10.3 80.8 98.0

Two-stage magnetic separation eliminated fine grinding of only 18 percent of

the total ore. Recovery of iron was slightly inferior to that obtained by direct

treatment of ore ground to minus-100-mesh. In addition, recovery of copper would

necessitate fine grinding of the minus-10-mesh reject, thus nullifying any possible advantage of the two-stage treatment. This method of concentration was not

investigated further.

Magnetic Separation Followed by Flotation

In an effort to produce separate marketable concentrates of iron and copper,

the reject from magnetic separation was treated by flotation in a series of tests.

Best results were obtained from ore ground to minus-100-mesh. The fine ore was

magnetically separated in a Davis-tube type separator to recover magnetite; the

nonmagnetic fraction was treated by flotation to recover chalcopyrite. Results obtained by this treatment of each of the three ores are shown in tables 8, 9, and 10.

TABLE 8. - Magnetic separation followed by flotation, Poorman

Metallurgical data

Weight, Assay percent Distribution, percent

Product percent Fe Cu Si02 S Fe Cu SiO2 S

Magnetic .............75.29 66. 0.10 4.9 0.2 90. 23.5 33.9 1

Cleaner concentrate. 1.75 39.4 10.1 2.2 43.0 1.3 55.5 - 22.1

Cleaner tailing .... 5.64 39.9 .69 76 41.0 4.1 12.2 3.9 67.9

Rougher tailing .... 132 12.0 .16 39.1 1.1 3.8 8.8 62.2 5.6

Calculated head .... 100.00 5^.7 .32 10. 3.4 100.0 100.0 100.0 100.0

Operation data

Grind: Minus-100-mesh

Dowfroth 250, frother.
11

TABLE 9. - Magnetic separation and flotation, Rush & Brown

Metallurgical data

Weight, _ Assay, ercent___ Distribution percent

Product percent Fe Cu SiO2 S Fe Cu Si02 S

Magnetic .... 77.27 67. 0 .20 23 0.95 9 1 4.8 28.2 31.1

Cu cl. conc.. 3.87 36.7 19.0 2.8 36.3 2.5 70.4 1.7 59.5

Cu cl. tail.. 1.09 29.8 4.4 17.6 9.8 .6 4.6 3.0 4.5

Ro tail ...... 17.77 T 17.5 .33 23.8 .65 5.5 10.2 67.1 4.9

Calc. head... 100.00 56.6 1. J 6.3 2.36 100.0 100.0 100.0 100.0

Operation data

Grind: Minus-100-mesh

Time, Reagents, ounds per ton of feed

Circuit minutes pH Na2Co 3 Z-6 D-2502 / R-301/ Met4/

Condition ............. 5 - 5.0 0.5 0.0 - -

Rougher ................ 4 9.7 - - .1 1.0 1.0

Cleaner ................ 3 8.5 - .1 - -

J Potassium pentasol xanthate.

Dowfroth f 250, frother.

American Cyanamid Reagent 301.

Sodium metasilicate.

TABLE 10. - Magnetic separation and flotation, Copper Center

Metallurgical data

Weight, Assay, percent__ Distribution percent

Product percent Fe Cu S102 S Fe Cu Si02 S

Magnetic..... 7.61 69.2 0.08 2.1 0.06 88.6 3.0 10.9 1.2

Cu cl. conc.. 6.20 35.2 23.5 .8 37.9 4.1 81.9 .4 66.0

Cu cl. tail.. 2.34 38.0 4.9 8.1 37.2 1.7 6.5 1.4 24.4

Ro tail...... 23.84 12.5 .64 47.8 1.1 5.6 8.6 873 7.4

Calc. head... 100.00 52.8 1.80 13.1 3.55 100.0 100.0 100.0 100.0

Operation data

Grind: Minus-100-mesh

Circuit

Condition .........

Rougher ............

Cleaner ............

2/

Potassium ethyl xanthate.

Dowfroth 250, frother.

Magnetic separation of minus-100-mesh Poorman ore recovered 90.8 percent of the

total iron in a concentrate that assayed 66.0 percent Fe, 0.10 percent Cu, 4.9 percent SiO2, and 0.2 percent S. The sulfur rejection was inferior to that obtained in

the corresponding test of a smaller sample (see table 4), probably due to overfeeding of the small separator during this test. Flotation of the nonmagnetic portion

of the Poorman ore resulted in recovery of 55.5 percent of the copper at 10.1-percent-Cu grade.

Similar treatment of Rush & Brown ore recovered 91.4 percent of the iron in a

concentrate that contained 67.0 percent Fe, 0.20 percent Cu, 2.3 percent SiOp, and
12

0.95 percent S. The copper flotation concentrate assayed 19.0 percent Cu; copper

recovery was 70.4 percent.

Magnetic separation treatment of the Copper Center ore resulted in a concentrate assaying 69.2 percent Fe, 0.08 percent Cu, 2.1 percent SiO 2, and 0.06 percent

S; the concentrate contained 88.6 percent of the total iron. Flotation of the nonmagnetic portion of the ore recovered 81.9 percent of the copper at 23.5 percent Cu

grade.

In general, copper and sulfur content of the iron concentrate was high in all

tests. This is attributed to the collection of locked magnetite-sulfide particles

in the iron product.

Flotation Followed by Magnetic Separation

In an effort to make a cleaner iron product by elimination of the locked magnetite-sulfide particles, a reverse treatment method was tried. Ore was ground to

minus-100-mesh; the sulfides were removed by flotation and cleaned to produce a

copper concentrate; the flotation tailing was magnetically separated to produce a

magnetite concentrate. Results are shown in tables 11, 12, and 13.

TABLE 11. - Flotation followed by magnetic separation, Poorman

.. ____.._Metallurgical data

Weight, Assay, percent Distribution, percent

Product percent Fe Cu SiO2 S Fe Cu Si0 2 S

Copper concentrate .. 0.88 35.3 25.1 1.9 38.7 0.6 69.3 0.2 10.1

Cleaner tail nonmag.. 6.58 41.2 .69 7.4 42.4 5.0 14.1 4.9 82.4

Cleaner tail mag. ... 1.36 61.0 .83 5.4 6.9 1.5 3.4 .7 2.8

Rougher tail nonmag.. 18.36 11.9 .11 33.7 .75 4.0 6.3 62.5 4.1

Rougher tail mag. ... 2.88 66.0 .03 4.3 .03 889 .9 31. . 6

Calculated head ..... 100.00 54.1 .32 9.9 3.39 100.0 100.0 100.0 100.0

Combined mag........ 74.18 6.04 4.3 .16 90.4 10.3 32.4 3.4

Operation data

Grind: Minus-100-mesh

Time, Reagents, pounds per ton

Circuit minutes pH CaO NaCN Z-31/ |D-2502/

Cu rougher .......................... 2.5 11.3 1.9 0.1 0.2 0.04

Cu cleaner .......................... 5 10.8 - .05 .1 .04

1/ Potassium ethyl xanthate.

Dowfroth 250, frother.

TABLE 12. - Flotation and magnetic separation, Rush & Brown

__________Metallurgical data

Weight, Assay percent__ Distribution, percent

Product percent Fe Cu SiO 2 S Fe Cu SiO2 S

Cu cl cone. ..... 2.70 34.9 246 3.~ 29.6 i.6 70. 1.3 36.2

Cl tail mag. ... 2.65 63.2 0.75 2.2 2.2 2.1 1.5 .7 1.9

Cl tail nonmag.. 1.89 35.6 6.2 7.9 20.1 1.7 17.4 3.3 24.1

Ro tail mag. ... 74.53 68.2 .10 2.8 0.9 88.9 8.0 25.5 30.4

Ro tail nonmag.. 18.23 17.9 .13 24.4 .9 .L 2.5 69.2 7.4

Calc. head ..... 100.00 57.2 .95 6.9 2.21 100.0 100.0 100.0 100.0

Combined mag... 76.42 68.1 .12 2.8 .93 91.0 .5 28.8 32.3

4
13

TABLE 12. - Flotation and magnetic separationB Rush & Brown (Con.)

a

Operation data

Grind: Mesh-100-mesh

Time, Reagents pounds er ton of feed

Circuit minutes pH Na2CO3 Z-6 1 D-2502 NaCN

Condition ......................... 5 - 2.0 0.3 0.08 -

Rougher ........................... 2 9.5 - -

Cleaner ........................... 1I.5 8.0 - - - 0.3

1/ Potassium pentasol xanthate.

g Dowfroth 250, frother.

TABLE 13. - Flotation and magnetic separation, Copper Center

Metallurgical data

Weight, Assay, percent Distribution, percent

Product percent Fe Cu SiO2 S Fe Cu SiO2 S

Cu cl conc. ........ 7.97 37.7 19.3 0.05 36.4 5. 87.2 - 77.0

Cu cl tail nonmag... 1.67 31.4 4.35 16.0 42.0 1.0 4.1 2.2 18.6

Cu cl tail mag. .73 66.4 .70 2.6 .9 .9 .3 .2 .2

Ro tail mag. ....... 65.48 70.3 .04 1.8 .06 86.8 1.5 9.6 1.0

Ro tail nonmag. .... 24.15 12.3 .50 44.8 .5 5.6 6.9 88.0 3.2

Calc. head ......... 100.00 53.0 1.75 12.3 3.75 100.0 100.0 100.0 100.0

Combined magnetic . 66.21 70.2 ,.02 1.8 . 7 87.7 1.8 9.8 1.2

Operation data

Grind: Minus-100-mesh

Time, Reagents pounds per ton of feed

Circuit minutes pH Na2C03 Z-61/ D-2502

Condition........................ - 2.0 0.3 0.08

Rougher .......................... 2 9.0 -

Cleaner .......................... 2 8.5 - - -

1 Potassium ethyl xanthate.

2/ Dowfroth 250, frother.

Flotation of Poorman ore, followed by magnetic separation of flotation tailing,

recovered 90.4 percent of the total iron in a concentrate that assayed 65.9 percent

Fe, 0.04 percent Cu, 0.16 percent S, and 4.3 percent SiO2. The cleaned copper concentrate contained 69.3 percent of the copper at 25.1-percent Cu grade.

By direct flotation of minus-100-mesh Rush & Brown ore, 70.6 percent of the

copper was recovered at 24.6-percent-Cu grade. Magnetic separation of the flotation

rougher tailing recovered 88.9 percent of the iron in a concentrate that assayed

68.2 percent Fe, 0.10 percent Cu, 0.9 percent S, and 2.8 percent SiO2. An additional

2.1 percent of the iron can be recovered by magnetic separation of the cleaner tailing; the combined product would assay 68.1 percent Fe, 0.12 percent Cu, 0.93 percent

S, and 2.8 percent SiO2.

By flotation, 87.2 percent of the copper in Copper Center ore was recovered in

a concentrate that assayed 19.3 percent Cu. Magnetic separation of the combined

flotation tailings recovered 87.7 percent of the iron in a concentrate that assayed

70.2 percent Fe, 0.05 percent Cu, 1.8 percent Si02, and 0.07 percent S.
14

In general, flotation followed by magnetic separation effected more complete

rejection of impurities from the iron concentrate than the reverse procedure. This

treatment is similar to that developed at the Rolla, Missouri laboratory of the

Bureau of Mines for the treatment of Mount Andrew ore .11 The Mount Andrew ore, however, responded to flotation after grinding to minus-35-mesh. Preliminary flotation

tests of Poorman, Rush & Brown, and Copper Center ores indicated that grinding to at

least mlnus-65-mesh is required to produce a tailing low in copper and sulfur.

As the bulk of the total ore would require regrinding to minus-100-mesh for

magnetic separation, it was decided that a simple 1-circuit grinding of all of the

ore to minus-100-mesh would be preferable to a treatment involving primary grinding

to minus-65-mesh, flotation, and regrinding of the flotation tailing.

Sintering

Preliminary sintering tests were run on concentrates made from the Kasaan

Peninsula ores, using a laboratory sintering machine to simulate plant practice.

Although exhaustive tests were not made, the sinters produced appeared to be similar

in fuel requirements, moisture requirements, physical strength, and reducibility to

those made from other magnetite concentrates.

The sintering operation alters slightly the chemical composition of the concentrate. The iron percentage is reduced slightly because of conversion of some magnetite to hematite and because of a minor amount of dilution of ash from the added

coke. Most of the sulfur is burned off.

Typical results obtained from sintering iron concentrate of the Kasaan Peninsula ores are shown in table 14.

TABLE 14. - Sintering results

Concentrate Sinter

Assay, pe As rcentAsay r t

Fe Cu Sib Cu S SiO 2 P TiO2

Poorman ............ 66.' 0.045 0.2 4.9 65.7 0.035 0.06 54 0.01 0.05

Rush & Brown ..... 67.2 .08 .78 2.8 65.9 .095 .15 3.5 /.01

Copper Center .... 69.6 .06 .06 1.5 68.1 .08. 03 2.4 -

1/ Less than.

Flowsheet

A suggested flowsheet for milling the ores is appended (fig. 3). The flotation

cleaner tailing could be rejected or stored for possible subsequent treatment for the

production of sulfuric acid and copper and iron byproducts. An alternate plan would

include magnetic separation of the original cleaner tailing; this would recover a

small amount of additional iron at the expense of grade. The nonmagnetic fraction

of this treatment could be either rejected or stored. The cleaner tailing or the

nonmagnetic fraction of the cleaner tailing should not be returned to the flotation

circuit, however, since it would result in contamination of both final concentrates.

11/ Work cited in footnote 6 (p. 2).
I

I

T

--

I I * f* .J>

Crushed ore

Ball mill

I ' Oversize

L Classifier E 0

4(Jl I

Minus-65-mesh ore

oher flotation I Rougher flotation|

I I

Concentrate Tailing

Cleaner flotation Magnetic separation I - . - Nonmagnetic

P I reject

Final

copper

concentrate

Cleaner tailing

if

F

Final

magnetic

concentrate

To waste

or

storage

Figure 3. - Suggested flowsheet. V-

^Jl

a