RI. 4512

was excavated in 109 hours operating time at a cost of $490.50, or 11.3 cents
per cubic yard.

Excavation by pick and shovel began on September 14, and trenches with an
average width of 32 inches were dug to bedrock. A portable air compressor and
accessory equipment were hired.on September 9 to operate a jackhammer that was
used to drill the bedrock to a depth of 2 to 3 feet, depending on how badly it
was weathered. Usually, holes were put in about 40 inches apart and broken
with 1-1/2 sticks of 40 percent dynamite. There was mch hardpan in the over-
burden, and this also was drilled and blasted.

Although four snowfalls and freezing temperature were considerable handi-
caps, all trenching was completed on October 30. Drilling and blasting were
finished on October 25, and the air compressor and accessory equipment were
returned to their owers next day. In all, 8,073 feet of trenches having
an average depth of 5.24 feet were dug. Longitudinal profiles of each of the
24 trenches are shown on figures 6 to 9. The total volume of mterial removed
was 4,182 cubic yards, of which 3,023 cubic yards were excavated by hand at a
total cost of $2,646 per cubic yard, .and 1,158 cubic ‘yards were removed by
pulldozer at a cost of 11.3 cents per cubic yard, or an average cost of $2,031
per cubic yard.

Trench Sempling

After cleaning the bottom of the trenches with brooms, continuous channels
4 inches wide and 2 inches deep, yielding about 10 pounds of sample per foot,
were cut along the bottom of the trenches except where pegmatite, metadiorite,
or other barren intrusives occurred. Sample cutting was done with single jacks
and moils. The cut mterial was gathered in powder boxes, from which it was
transferred to closely woven burlap sacks holding 50 to 60 pounds each.
Melting snow and infiltration of water from surface springs sometimes made it
necessary to bail portions of the trenches, and where the samples contained
too mch water they were dried in tubs over the Dutch oven used for drying
and sludge from the diamond drills.

As far as possible the sampling intervals were made to conform with the
geologic units in order to determine the distribution of the chromite with
respect to the various types of rock. However, in a few instances individual
samples embraced portions of formations that showed slight differences in
mineralogical composition, The number of such samples was insignificant com-
pared with the total number taken, and the differences in composition between
rocks included in the same-sample were in general so minor as to be distinguish-
able only to a trained geologist. In a few instances, narrow streaks of notably
different rock were included in the same sample, but these streaks would
necessarily have to be mined with the surrounding rock.

In general, the trenches disclosed a great many rock units as well as
great variation in the character and amount of alteration and weathering within
single units. Usually the sample interval was 5 or 10 feet, and only 12 sample
intervals exceeded 10 feet and none more than 13 feet. A galvanized-iron shed
was erected at 1W 1N to store samples where they could be kept dry and safe

3047 -8-


BT. W512

taj Interval, Core recovery Weight, “ams Footage interval, Core recovery Weight. ams
fo feet _ Inches Percent Core Sludge Description Fron To__feet___Tnehes Percent tre sides Description

351 -385,5 2.5 20 66 —-383.-«S 838s Granite-pegnatite, 557.3 563 5.7 60 88 697 1,555 Gray-green tale-actin—
333.5 339 5.5 60 sl 1,278 320 do, olite schist with
3392 3 24 66 «858 = 460 do. chromite,
342034 2 uu 59-253 67 do, 563 5685 5,5 39 59 881 992 do.
3449 5 44 73° 975148 do, 568,5 571.5 3 36-100 946 435 do,
349354 5 54 90 1,120 278 571.5 573 150 61 isl 647 do,
354358 4 33 69 "630775 573 580 7 26 31 551 1,779 From 578 granite
358363 5 60 100 1,337 865, pegmatite,
363368 5 60 100 1,340 566. 580 583 3 26 ic 448779 do,
368872 4 36 75 684 485
372875 3 aL 86 639 S10 Hole 4 Bearing: 5, 30° 2,
375 380,555 GL. 93 (1,328 © 154 Location: 700 W., 130 N, Dip: 40°
360.5 386 5.5 40 61 1,835 = 375 Elevation at collar: 8,067.3 Depth: 389.1 feet
386-392 6 65 90 1,220 407 From 390,5 gray-green
tale-actinolite schist Oo 38 38 ° ° ° 0 Soil and unconsolidated
with chromite, rock,
392397 5 a 69 1,69 716 do. 3385 2 12 50 160 0 Weathered amphibolite,
397 © 402 5 60 100 1,799 1,143 3536 1 9,6 80 230 0 Actinolite-tale schist
402 408 1 Lost core 630( 4 209 with chromite,
403 406 3 32 89 1,450( “? 3639 5 1s 50 8700 do,
406 all 5 59 98 1,450 1,575 3946 7 18 21,4 350 5,640 do,
a 416 5 54 90 1,370 2,991 46 49 8 33,6 93,3 800 3,233 Granite pegmatite,
46 421 5 59 98 1,423 2,000 49° 54 5 18 30 4202, 533 do,
421 426 5 60 100 1,587 2,871 5459 5 18 30 © 340. -4,088 do,
4260 451 5 60 100 1,614 1,785 5964 5 21.6 35 490 3,012 do,
43L 4365 54538 58 6 788—«1,350 64-66 2 20.4 85 -520( 5g), Tale-mica schist,
436.5 442 55 57 86 1,120 1,351 6669 3 27,6 76.7 380( “?°"* Tale-mica schist and
442 6 58 81 1,655 “835 vermiculite,
448 453 5 37 6 7430S 781 69 70.5 1,5 15,2 73,3 210g aq &
453° 458 5 33 55 659835, 70.8 75 4.5 25.8 44,1 340( >? oe
458 462 4 24 50 510986. 75 84 9 39,6 36,65 850 7,069 Metadiorite,
462-467 5 49 82 1,028 2,770 84~ 90 6 6 +834 120 9,790 do,
467472 5 45 75 1,035 1,795 9 91.5 1,5 18 100 520 4 sng do.
472477 5 48 80 "901995 91,5 92.5 1 9.6 80 220( * *
477 482 5 60 100 1,418 1,050 92,5 94 1,5 ° ° ) ° do,
482 487 5 56 93 1,399 1,281 4 98,5 «64,5 50 55.5 740( 5 sag do.
487 492 5 38 63 867 961. 98,5101.5 38 30 83.3 710( > .
492 496,545 44 85 1,033 1,412 101.5 1065 5 60 100 1,600 2,385 do,
4965 SOl.1 5.4 61 94 1,517. 1,737 106,5 112 55 36 54,5 "900 796 do,
501.1 507.5 5.8 60 86 1,551 2,246 nz 16 4 25.4 52,9 630 1,386 do.
507.5 S18 5.5 49 74 1,438 1,207 m6 121 5 34,8 58,0 670 1,745 1 in, metadiorite,
513 518 5 60 100 429 «1,466 4 in, actinolite-tale
518523 5 27 45 «363 648 schist, with chromite,
823 525 2 24 100 192 Sah 121 1265 55 18 27,25 370 1,717 Actinolite-tale schist
525-550 5 56 93 1,392 1,279 with chromite,
530 B82 2 24 100 685 687 126,5 131 4,5 25,4 47 450 5,400 do.
532 «538 6 60 86 1,016 1,417 isl 156 5 18,7 31,2 330 5,657 do,
S88 542,242 4B. 89 "940 1,065 isé 141 5 13,2 22,0 250 3,956 letadiorite,
542.2 546.6 4.4 52 99 1,462 1,412
546.6 551.8 5,2 59 95 1,552 1,571
551.8 557.3 6,5 58 74 "7991, 515

3047 -19-


RAI. W512

Sample Interval, Fercent © Sample Interval, Percent rent
No. Trench feet CreQy No. Trench __ feet Cr20; No, __ Trench feet. Cra,
391 3B 10 1,84 441 SE 10 0,92 491 8B 10 0,78
392 7 2,15 442 10 1.84 492 5 205
398 6 2,00 443 4 2.51 495 10 205
394 10 05 444 10 2.41 494 10 10
395 8 205 445 10 2.84 495 20 005
396 aE 8 205 446 lo 2.41 496 10 230
387 65 1,02 447 8 2,28 497 10 1,28
398 10 +3 448 8 2.33 498 10 31
399 10 +51 449 7 2.82 499 10 215
400 10 1,59 450 10 4,10 500 10 228
401 10 174 451 10 4,07 50L 10 218
402 10 2,56 452 10 2,41 502 10 “74
403 10 1,54 455 10 1.77 503 10 233
404 7 2625 454 lo 1,79 504 n 210
405 10 2.20 455 10 aL 50S 10 23
406 10 272 456 6 1,28 506 e 6 205
407 10 +41 457 2 5.53 50? 7 38
408 6 +56 458 5 +3 508 10 35
409 2 236 459 5 +95 509 5 260
4210 10 1.74 460 5 205 510 6 260
a1 10 2,66 461 5 205 Bl 10 205
a2 10 2.15 462 5 205 512 10 205
413 10 87 463 2 87 513 10 205
44 10 +20 464 6 9.73, sl4 10 206
415 6 46 465 5 8,09 515 4 5,00
416 10 2,10 466 5 2,00 S16 7 4,50
417 6 1.54 467 5 +10 517 6 4.20
418 8 74 468 5 2,92 518 10 6.10
a9 9 2.10 469 5 3.60 519 5 5.70
420 6 3.64 470 5 7,80 520 7 11,10
421 2 1,46 4am 5 4.40 521 7 3.07
422 10 4,04 472 5 205 522 6 3.15
423 10 2,73 473 5 1,20 523 10 233
424 6 8,70 474 5 1340 524 10 S18
425 6 14.75 475 5 +30 525 5 +10
426 6 2.10 476 5 +30 526 20 18
427 10 1,79 477 5 1,80 527 10 «18
428 10 1.23 478 5 1,60 528 10 238
429 R 1,13 479 10 +80 529 10 228
430 v 1,33 480 10 1,30 550 9 226
431 10 +61 481 10 1.08 Sal 7 233
432 9 3,84 482 6 97 Bs2 10 344
433 10 2,36 485 8E 4 205 eas rq ry
434 7 3.99 484 10 05 $34 e 20 305
435 10 10,19 485 10 205 535 10 205
436 10 1,64 486 10 +05, 556 20 05
437 10 «10 487 4 4,45 $87 0 S05
438 10 3.94 488 10 3.17 $58 10 205
439 7 2210 489 10 18,43 559 10 $20
440 SE 10 156 490 10 3.64 a0 0 220
sou “15°

Sample Interval, Percent
No, Trench eet, Cro,
sal 10 0,20
542 5 605
545 10 220
544 6 05
545 8 210
546 20 +10
547 7 10
548 7 05
549 7 05
550 10 4.80
551 20 5.50
552 5 7,00
555 5 7,00
554 5 4,70
555 20 7,80
556 6 2,10
557 10 30
558 10 05
559 10 230
560 4 +30
561 5 «20
562 20 re)
565 5 1,00
564 5 220
565 5 220
566 20 220
567 10 205
568 9 40
569 10 290
570 10 50
s7L 8 220
572 7 220
573 7 220
STA 8 1.9
575 10 2.60
576 10 +20
S77 10 005
578 10 7,20
579 6 19.50
580 6 25,50
581 5 26,50
582 6 22,50
585 5 5.80
584 10 +70
585 8 270
586 10 5.40
$87 10 2,70
588 7 2,90
589 8 1.40
590 20 1,50


RoI. 4512

Footage Interval, Core recovery Weight, grams Foota; Interval, Core ~ recove: Weight, grams

Fron To__feet Inches Percent Core Description Fg tiens “teot” Inches Percent Core Sindee: Description

505 506 1 7 58 98 Black basic dike, hard, 678 682 4 Ere nm 761 Silicified schist
dense, (hornblende schist’),

506 507 1 1 100340 do. 682686 4 28 58 654. do.

507 508 2 u“ 58274 do. 6R6 691 5 35 5B B52 do.

509 512,535 27 6 SBL do. ssl 696 5 44 73 1,046 do,

512,5 516 35 16 38-509 Fron 510-1/2 to 530, 696 701 5 23 38536 do,
pegmatite, 701-706 5 27 45 629 do.

S16 522 6 7 97 10g do, 708 710 4 2 4 15 do,

522 826 4 7 aes 95 do. no 7 1 15 12 19 do.

526529 3 29 8 486 do. mm 71? 6 19 26 360 do.

529 532 3 7 47 267 From 530 to 540, schist n7 719 2 15 62 a4 Granite pegmatite with
and vermiculite, highly altered tale actinolite
altered, silicified in schist,
part, 9 724.5 5.8 30 45 0 «672 Granite pegmatite with

582 (556 4 3 67 02 . altered tale actinclite

536 540,85 4,5 58 98 1,144 do, schist inclusions and

540.5 544 350 (18 43 5 Granite pegmtite, vermiculite,
variable, with inclus- 724.5 730 5.5 66 100 «1,426 de,
ions of highly altered 730781 1 8 67 130 do.
schist and vermiculite, 731736 5 48 80 1,071 do.

544 550 6 8 nous do. 736 741. 5 56 93 1,358 do.

550 585 5 25 42 425 do, 741 746 5 56 93 1,429 do.

555 «557 2 8 30155 do, 746 781 5 52 87 1,238 do.

557 558 1 7 58 80 do, 751-755 4 28 58589 From 751 to 758, pink

558 563 5 42 70 755 do, pegmatite,

563 «569 6 22 Sl 435 a, 755 760 5 45 78 983 do,

569 «575 6 59 82 1,910 do. 760-765 5 50 50636 Fron 758 to 772, fine

575 580 5 32 4 0 do. grained tale actinolite

580 584 4 16 33 330 do. schist,

564 589 5 60 100 1,150 do. 765 771 6 39 54840. do,

589 594 5 60 100 1,117 do. 7 «778.5 445 87 69 495 From 772 to 786,

594597 3 36 100-290 do. pegmatite,

597 605 6 37 79 1,220 do. 778,58 781 5.5 28 35600 -

603 608 5 40 67795 do. 7a 786 5 sl 52 600 do.

608 618 5 58 96 1,145 do. 786-792 6 63 88 1,570 Green schist in part

613-618 5 60 100 1,260 do, silicified pegmatite

618 623, 5 53 89 1,010 do, inclusions,

623-628 5 37 95 1,170 do. 792-796 4 7 35 806 do,

628 630 2 20 83450 do, 796 802 6 63 88 1,439 do.

630-636. 6 55 76 1,490 do. 802 804 2 No core

636642 6 60 83 1,522 do. 804 Bll 7 29 35 «509 do,

642648 4 43 90 1,082 do, ml 816.5 5,5. 6 9 ia do,

646 «651 5 36 6 872 do, 1.5 822 5.5 Be 52 592 do.

651 «656 5 60 100 1,515 do, 822 827 5 21 35 (369 do.

en ee 70 1,044 do, 827 882 5 20 33302 From 826 to 637, hard,

661.5 666 4.5 2h 39357 do, black, dense rock,

670 4 8 7 135 do, e32-835 5 18 50387 do,
670 678 3 12 33-287 do. 885838 5 33 50 602 From 837 to 840-1/2,white
673 «678 5 42 70 2,023 do, quartz with much biotite,
838 840.8 2,5 = 30 100 482. do,
840.5 844 BS ze 29 92 Granite with muck biotite,


RI. 4512

having an area of about 3.7 acres. Figure 4 is a contour map of the area.

The locations of all trenches and diamond drill holes and of the road cut
sampled are shown on figure 5, which also shows how closely the boundaries of
the larger lens, as determined by the magnetometer survey, coincide with those
disclosed by trenching.

Work at the deposit began on August 23 with five men, who started staking
trench lines and preparing diamond drill sites. As the work progressed, this
crew was gradually increased until, on October 5, it reached a mximm of 56
men, who were engaged in trenching, trench sampling, and attending to the cores
and sludges from the diamond drills. In the meantime, mch work of a general
nature had been accomplished. A narrow trail running through the woods on the
west end of the larger schist lens was widened into a 12-foot road between 1E
and 13E (fig. 5), a distance.of 1,450 feet, to serve as a main east-west
thoroughfare giving access.to the trench sites. Two springs were dug out to
develop a.water supply for diemond,drilling, and, on finding that their com-
bined flow was inadequate, an.earth dam was built across Elkhorn Creek to
impound water for the same purpose, Diamond-drill sites for holes 1 to 6 were
cleaned of their dense timber, and roads and trails were cut to them from the
main east-west thoroughfare. A galvanized-iron shed housing a 3- by 5-foot
Dutch oven for drying diamond-drill, sludges was erected at 7W 1.5N, and a
sample house for the dry storage and safe keeping of trench samples was built
at 1W 1N. Arrangements were made with the City of Caspor for the free use of
two stone buildings in the neighboring city park in section 16, one for a
carpenter shop, where core boxes, benches, office furniture, tool boxes, and
other equipment were made and in which all diamond-drill cores and sludges
were weighed and stored, and the other as 4 magazine for dynamite. On .
September 13, an unfurnished office in the Consolidated Royalty Building in
Casper was hired for 3 months at $25 per month and equipped with furniture.

. The diamond drilling was let under contract by the Bureau of Mines to
the Diamond Drill Contracting Co. of Spokane, Wash., which installed two drill-
ing rigs on the property early in September and a third on October 23. This
company furnished its own drill crews and a drill foreman under whose direc-
tion drilling was done on two or three 8-hour shifts daily, as conditions
warranted, A caterpillar winch for pulling stumps, an air compressor and
necessary equipment, and a bulldozer were hired to facilitate trenching opera-
tions. Men were transported between Casper and the deposit in a 1-1/2-ton
Ford truck with a platform and stake body. When more than 30 men were em-
ployed, it was necessary to make two trips to carry them, one crew leaving
Casper at 6:15 a.m. and the second crew at 7:30 a.m. An 8-hour shift was
worked, two foremen and the truck driver receiving 75 cents an hour and the
rest of the men 62.5 cents per hour.

All tronching was completed on October 30, and trench sampling was
finished. the next day. On November 1 the crew was reduced to 12 men and on
November 8 to 5 men, who were retained to handle diamond-drill cores and
sludges. Diamond drilling was completed on December 3, and the backfilling
of trenches and diamond-drill sites was finished on December 6, which com-
pleted the work on the deposit.

30k7 -6-




RoI. W512

Footai Tnterval, Core recovery Weight Footage Interval, Core recovery Weight. is
Fron foot” Tnohos Percent oe ‘stnage Description Fron" fect.” Tachas Percent _Care “Statue Description

141146 5 42 70  820«-8,053 Netadiorite, 334,5 340 65 60,5 91,61,487 2,665 Green schist or ser—
146 148 2 20.4 85 390 3,884 do, pentine and chromite,
14g 158 10 0 0 3, 5,048 No core recovery, 340 34d 4 a 85.5 962 4,479 do,
158 160 2 18 75 310! 344349 5 60 100 1,480 3, 822 do,
160 163 3 28.8 80  580( 49587 Metadiorite, 349354 5 60 100 1,350 3,038 do.
163 168 5 20 280 4,167 354 357 3 25 69.5 "528 2,505 do,
168173 5 40.8 68 790 3,917 357359 2 24 100 5802, 485 do,
173178 5 60 100 1,440 1,635 359364 5 4 56,7 722 1,695 Actinolite-tale schist
178 183 5 “8 58 7101, 928 with chromite,
183 188 5 54 20 1,010 2,890 364 369 5 a 56,7 609 2,580 do.
188 193 5 40.8 68 1,000 3,110 do, 369374 5 40 67 = 608.1, 575, do,
193 199 6 38,4 53,4 870 5,180 Actinolite schist with 374877 3 36 «100787 1,775 do,
chromite, 377381 4 45 98.7 1,041 3,490 do.
199 204 5 37.2 62 740 3,145 Actinolite schist and 361 383.25 2.25 12 44.45 208 973 do.
chromite, 385,25 384,75 1,5 15 83.3 280
204 209 5 25.2 42 470 4,340 do. 384,75 386,75 2 ie 66.7 340( 9978 conn vermiculite
209° «814 5 57.6 96 1,090 5,480 do, 386,75 389.1 2,3 ° 0 ° 124 ‘do:
aa 219 5 43,2 72 3,347 do.
219 223 4 39.6 82,5 910 1,775 do, Hole 5 Bearing: 5, 30° E,
225° 228 5 37.2 62 760 5,156 do. Location: 9.50 W., 2 N, Dip: 40°
228 229 1 4,8 40 20 oO do, Elevation: 8,081.6 Depth: 379 feet
229 254 5 20 34 «470-6 430 Metadiorite,
254 287 3 144 40 820 978 Talc-mica schist, Oo 9 Overburden and badly
257 241 4 15.6 82,5 500 1,850 Metadiorite, weathered quartz—aica
241 246 5 96 16 220 6,750 Talc-mica schist, schist,
246 249 3 15.6 45,3 340 4,460 Metadiorite, 2 942 22 18 68 -340(
249 254 5 42 70 ©9708, 740 do. 94.2 99.3 5.1 10 16 -200( 2396 Quarta-mica schist,
254 256 2 18 75 460( 5 755 do. 99,3 102 2.7 18 55 308 330 do.
256 259 3 20.4 56,6 490(  ~? . 102-107 5 30 50 585 2,530 do,
259 264 5 18.2 22 280 3,830 do. 107s 5 4 23 2251282 do.
264 269 5 80 50 620-8, 780 do, uz. 7 5 20 330 Bll 274 do,
269-274 5 39.6 66 870 5,825 do. 117.5 120 25 18 60 314 +398 do,
274 «279 5 60 100 1,360 5,375 do. 120125 5 26 43 530 2,210 do,
279 282.5 3.5 38.4 91,3 860 5,490 do, 125 128.5 5,5 26 62 486 554 do,
282.5 285, 3 34.8 96,6 950 535 do, 128,5 133 4.5 17 Bl «815.2, 525 Granite pegmatite,
285,5 268,5 3 24 66,7 630 680 do. 1330-138 5 30 50 720 7,084 do.
288,5 292 3.5 39,6 94,51,160 1,585 do. iss 143 5 28 46 470=« 4,912 do.
292° 294 2 21.6 90  690( 5 og do. 1430s. 5 0 © No core 6,008 Altered quartz-mica
294 298 4 42 27.5 1,150( 5515 Green schist or ser- schist (7
pentine and chromite, muss 1 pt 100-215 No do,
298 300 2( 24 50 «61S «1,415 do, sludge
300 302 2¢ 2,730 do. 149184 5 ° © No core 5,215 do.
302 306 4 46 96 1,700 1,800 do, 154159 5 a 68 do, «3,567 Quartz~mica schist,
506 312.5 6.3 24 31.8 660 3,345 do. 159-164 5 48 80 1,131 4,837 Gray-green actinolite
312.3 318 7 39 2,700 do, (2) schist with
313.318 5 38 63,4 880 4,340 do. chromite.
318 524 6 95 15,8 185 3,735 do, 164 170 6 13 18 2918, OLS do,
B24 329,555 AL 62,1 935 1,515 do. 170176 6 e 86 1,384 4,229 do,
329.5 334,5 5 31,5 52,5 780 2,645 do, 176 =—«182 6 47 66 990 8,726 do.

3047 - 209


35

NORTH CASPER RIVER DRIVE & PARK
aA 2
amass =

CASPER MOUNTAIN PARK

“| Léadville- N

~ 31 36 |

31

R78W

R80w R79W

12.3 46 5 6

SCALE OF MILES

Figure |. - Index map showing location of Casper Mountain chromite deposits,
Natrona County, Wyo.


Re 12

APPENDIX Sample Interval, Percent © Sample Thterval, Percent

Analyses of Trench Sampl No. Trench feet, CreOy No, Trench feet Cr20;

Sample Titeral, Tercent © Sangls Percen % a 7 O82 La. Bi 10 0.

No, Trench feet Cra05 Ne. Trench ores Be Fria +33 142 10 en
1 . 143 10 298

1 TA 8 0.60 46 6i 10 0.41 % 20 1.12 144 10 ies
2 10 47 8 196 6 20 +85 145 10 Lis
3 5 46 ar 1.01 a” 30 77 146 10 1.78
4 8 49 12 11s 9a 20 “79 147 10 un
5 6 50 sw é 135 2 20 +72 148 10 lio.
6 7 sl 10 lize 100 20 2 149 10 118
7 7 52 10 3.07 tor 20 +55 150 10 110
8 6 53 10 192 6 20 +70 1st 10 lo1
9 9.5 54 10 19 208 19 +88 182 10 +79
10 5,6 55 10 173 108 8 1.14 153 10 i79
n 5.1 56 20 iol 204 7 2.46 154 10 tee
1 210 57 10 196 105 10 1.62 155 10 288
13 5.8 58 io ve 306 10 114 156 20 1,45
14 1s 58 8 3.88 107 5 16,02 1s? 10 2285
1s 5 60 8 228 208 5 11,23 158 10 1.0L
16 10 61 8 383 209 10 5.47 159 10 283
17 10 6 8 «83 210 n 1,80 160 7 1.40
18 9 63 9 292 im BH 5 1,49 161 wi n 218
19 10 64 10 +33 ne 20 +85 162 10 261
20 2,7 65 10 1.25 13 do +75 165 10 79
ca 10.3 66 10 15 14 10 +79 164 10 lon
22 10 67 10 1,12 ns 7 R624 165 10 61
23 6 ee 10 350 16 7 224 166 10 3,69
24 ew 10 69 10 1.29 n7 10 1.10 167 10 1.36
25 10 70 10 1.58 118 10 1,54 168 10 1.18
26 10 mn 10 282 ng 10 268 169 10 1,45
a7 10 mR 10 188 120 10 281 170 10 1.80
28 10 73 10 vie 121 10 +81 in 10 1.23
29 10 74 12 110 122 10 1,54 172 10 129
30 10 15 10 318 123 10 88 173 10 239
aL 6 76 10 172 1e4 10 1,01 174 10 294
32 5 77 10 4,48 125 10 1.27 175 10 -57
35 10 2 10 199 126 10 1.45 176 10 294
kc 10 79 e@ 64 127 97 270 177 10 294
35 7 eo aw 10 235 128 10 479 178 10 2.23
36 10.3 81 10 255 19 10 83 179 10 1,02
37 10 82 pal 8,03 130 6 97 180 10 «70
38 10 83 10 8.34 131 6 275 lel 10 72
39 10 94 10 1.89 152 8.5 +70 182 10 2.49
40 10 85 6 lcs 135 8.5 61 183 20 2.53
41 10 86 6 1,27 134 0 1440 184 10 8,29
42 10 87 10 118 135 10 +83 185 10 253
43 10 88 10 +8 156 5 1.26 186 10 44
44 10 89 10 15s 137 ai 10 +81 18? 19 5.9
45 10 90 2.9 231 158 10 +74 188 10 1.32
189 10 2.12 188 10 1,10

»H 140 10 1.80 190 ac 3.07

-13-


Sp Stare

gearerbrerir ese ey
enna pees .
pod aa aaa
Section
“we ee ec hebepeehatatipay ir Bt berber et
cgenenent ERECT 77
x wane EES
ger Br B85 ~
rasnscoo opehet? _
. i il i ‘ | i a i a F i
‘Sample Section through Trench IE
qd a-8-8-4-3-2-
gaged bette etre
eee sooo
i F ] 4 F 7
‘Sample Section through Trench 2 E -
—a er agence rks piy ito
eeactetennn REET a
sepagen reer
seve poe ie i cvs
q a q F q
Fd RAbAsihA Raab a bl ft Lia —
: “ “SCALE OF FEET
J oa oa 4

Somple Section through Trench 4€

Figure 6. - Sections through trenches 0 and IE to 4E, showing locations

of samples.



rth

ceeters a

Somple Section through Trench 10 W

A s+8 a
pesetéth eee

Jeeves 94 F 3 a Ey a curv vote |

Sample Section through Trench l2 W

snanswasannegeetet es Ts
ante # E Fl i i orn

‘Somple Section through Trench 13 W

dened |

i i

Somple Section through Trench |4 W

2806

eusv. 080 e100 |

anime i
Sample Section through Trench || W

a ee ee
‘SCALE OF FEET

Figure 9. - Sections through trenches 10W to I4W, showing
locations of samples.


peat apeyerererereeee eT ET

jion through Trench 6E

iimab

oosrepbrar bee re eee

—

ne en ee

reperereysih refer
Thi Pfo

ee ada

epee renee

acme i _#

Slee ree

“Sample Section through Trench 9E

g ~o »
a

Figure 7. - Sections through trenches 5E to 9E, showing locations of samples.



Bole 12

le rval, Percent Sanple Tnterval, Percent Sanple Trtervel, Percent © Sanple Thterval, Fercent
No, Trench ___ feet Cra05 No, Trench _ feet Org05 No. Trench __ feet, org, Nos ch feet, Grg0
si Ww 10 17 241 0 10 aa 291 2B 10 0,82 341 ww 6 0.77
192 20 1.58 242 10 131 292 1s 10 342 3E 5 226
193 10 1,36 245 10 2,49 293 10 343 10 2,70
184 10 4,91 28g 10 5 294 10 344 10 2.04
195 10 245 10 295 19 345 10 ie
196 10 246 28 10 296 a 346 10 12
197 10 247 10 297 10 347 10 2.65
198 10 248 10 298 10 348 10 1,79
199 7 249 10 299 10 349 10 2,96
200 ° 8 250 10 300 10 350 10 2.50
201 10 251 10 301 10 351 10 261
202 10 252 10 302 10 352 10 6,89
208 10 253 10 03 10 353 lo
204 10 254 lo 304 10 354 10
205 10 255 10 305 10 355 10
208 10 256 10 306 10 356 10
207 10 257 10 307 10 357 10
208 10 258 10 308 10 358 10
209 10 259 10 309 10 359 10
210 10 260 10 310 20 360
21 20 261 10 all 20 361 8.5
212 10 262 10 al 10 362 8,5
213 10 265 10 313 10 2.61 363 6
214 10 264 10 314 20 4.43 364 8
21s 10 265 10 315 1e 3.47 365 6.5
216 10 266 10 316 5 1,58 366 7
217 5 267 10 317 10 214 367 6
218 5 268 10 318 10 2.14 368 7
219 10 269 10 319 10 3,01 369 10.5
220 10 270 10 320 20 1.19 370 1
221 10 271 20 321 10 +56 371 9
222 10 272 10 322 10 102 372 10,5
225 10 273 10 328 10 205 373
224 10 274 10 324 10 +51 374 10
225 5 275 10 325 10 3,82 375 8.5
226 10 276 10 B26 10 1,07 376 7
227 10 277 10 527 10 28? 377 10
228 10 278 10 328 lo 297 378 10
229 10 278 10 329 10 +58 379 6.5
230 10 280 10 330 10 1,84 380 6
231 10 281 10 331 10 1.17 381 10
232 10 282 10 352 10 77 382 10
233 10 283 10 338 0 loz 385 10
234 10 264 10 334 20 +66 3e4 10
235 10 285 10 335 10 166 385 6
236 10 286 10 36 io te7 386 10
237 10 287 10 337 10 107 387 13
238 10 288 20 338 10 1,46 388 10
239 10 289 10 339 10 122 389 10
240 10 290 10 340 10 156 390 10





RI. 4512

This lens is intruded by irregular masses of both granite and metadiorite,
and diamond drilling has shown that the width and frequency of these intrusions
increase with depth. The maximm depth to which the schist extends is unknown,
but drill hole 7 has proved its presenco. to a vertical depth of at least 500
feet. Because of the extreme irregularity of the lens, it is impossible to
determine its volume, oven approximately, from the data at hand. The schist
is cut by basic and granitic dikes, probably derived from the granite and
metadiorite.. These dikes are generally narrow, ranging from less than 1 foot
to about 10 feet in width, The granite-pegmitite dikes usually occur at or
near the granite contacts of the lens.

Tho schist is foliated parallel to ite dip and has in general been deeply
weathered, the steeply dipping foliation cracks affording easy access to
water and other weathering agencies. In the work done by the Bureau of Mines,
this deep weathering of the schist made it necessary to case diamond-drill
holes for a distance of 50 to 100 feet from the surface, and it was often
necessary to excavate trenchés to a depth of 10 feet before consolidated rock
was uncovered. :

MINERALOGY

The chromite-bearing schist was originally an ultrabasic rock, probably
peridotite, which has been metamorphosed to its present form by’ serpentiniza-
tion followed by steatization. The principal minerals composing it are
actinolite, trémolite, chlorite, talc, and chromite, but it also contains a
few other secondary minerals such as vermiculite, asbestas, a little hematite,
and minor serpentino.

Tho succession of tremolite-chlorite-tale is well kmown in the steatiza-
tion of ultrabasic igneous rocks and serpentine by younger acid intrusions
such as occur in this deposit.2

The chromite occurs as disseminated grains throughout the schist in
sufficient quantity to give it an average content of approximately 2 percent
Crp0z. These grains, however, are often concentrated in lensos, stringers,
and bands of considerable width that occasionally contain 5 to 25 percent
Crp0z. Usually these richer bands are roughly parallel to the contacts of
the schist lens. The chromite also occurs disseminated in flattened nodules
or pods resembling large avgen from 1 or 2 inches to 2 feet in thickness.
Figure 3 is a photograph of such a pod taken by B. L. Stephenson of the United
States Geological Survey. According to Diller,2/ 9 distribution of the
chromite similar to that in this deposit is characteristic of deposits believed
to have been formed by early crystallization of the chromite from magma.

5/ Hess, H.H., The Problem of Serpentinization and the Origin of Certain
Chrysoltile Asbestos, Tab, and Soapstone Deposits: Econ. Geol,, vol.
28, 1933, pp. 634-657.

6/ Dillor, J. S., Recent Studies of Domestic Chromite Deposits: Trans.,
A.I.ME., vol. 63, 1919, p. 120.

3047 -he-


RI, 4512
It is certain that the softer and mre friable portions of the schist
contain less chromite than the harder parts, In other words, the schist seems
to be strengthened by the chromite. Therefore, partial cores should always -be
richer than their corresponding sludges, as they were in the’ samples analyzed.
Panning tests showed that where no core was obtained, the sludges contained
virtually no chromite.

RESULTS or INVESTIGATION
The locations of trench samples are shown on the sections on figures 6 to
9, and the enalyses are given in appendix A. Table 3 gives a list of samples
containing over 15 percent Cr20s, and table 4 between 10 and 15 percent Crp030

TABLE 3. - Samples containing over 15 percent Cro0z

Interval, Percent
Sample No. Trench feet Crp0z
Bliccccvoccsvcceccvecse OW 6 17.35
ew 5 24.05
iw 5 16.02
OE 6 19.50
SE 6 25.50
95 5 26.50
9E 8 22.50
1lW 5 22.90
1OW 5 16,69
10W 7 21.25
lew 1 24.90
éw 10 13.63
iw 5 11.23
2E 10 14.09
ay 10 14.30

TABLE 4, - Samples containing between 10 and 15 percent Cre03,

Interval, Percent
feet Crg0z
6 1h.75
10 10.19
1 11.10
10 12,10
10 11.50
>) 10.40
5 10.00
~5 12,20
O86. ce ccenceeee 5 10.00
CBT oasarcececcsccrcessssese | LW 5 10.20

3047 : -l-




meheesisetce

890
SCALE OF FEET

LEGEND

AMPHIBOLITE

=
QUARTZ SCHIST

b
2
8
fas
w
Sow
ae
= 2
é
c
26
Nig
SS Ea

SERPENTINE

PALEOZOIC SEDIMENTARY ROCKS

METADIORITE

INS

Figure 2. - Map of areal geology, Casper Mountain chromite deposits.




RI. u§le

Eight thousand and seventy-three feet of trenching and 3,623 feet of
diamond drilling were done, and 1,644 samples were taken. A total of 1,920
man shifts was worked on this project by day labor with an average crew of
20 mon and 96 working days. Total wages were $9,938.20.

_ Trench:

Twenty-four parallel trench sites having a total length of over 8,000
feet were laid out at right angles to the strike of the larger schist lens;
these sites coinciding with the 100-foot intervals of the magnetometer survey
and bearing S, 30° E, The positions of these trench sites with reference to
the magnetometer grid and the schist lens are shown on figures 4 and 5. From
a zero point on the line between sections 16 end 17, the trench sites to the
west were numbered consecutively from IW- to 14W and those to the east from 1E
to 9E. . nts

As. agreements had been made with the City of Casper and. the Wyoming Baptist
Convention to refill all trenches on their property after sampling was com-
pleted, it was necessary to clear the timber from the trench sites for a minimm
width of 10 feet to provide room for piling the excavated material where it
could be backfilled with a bulldozer. Such clearing also allowed the use of
@ bulldozer in removing the unconsolidated overburden at a great saving over
doing it by hand. The interlocking roots of the closely growing pines formed
@ matlike notwork, which made excavation difficult, and, lacking a powerful
bulldozer such as a D7 or D8, the cheapest method of removing tho timber from
the trench sites was to cut it, leaving stumps 5 to 4 feet high, and then to
pull the stumps, piling them with the tree trunks along the sides of the trench
sites. Several thousand lodgepole pine trunks wore later used for building
windbreaks on a C.C.C. project ‘in Casper. By pulling the stumps, all bother-
some roots were removed. Stump pulling was done with a caterpillar winch
hired at $7 per hour of operating time. The work began on September 1 and was
completed on September 12, About 3,250 stumps Were removed in 54 hours operat-
ing time at a total cost of approximately 21 cents each.

The high speed and low cost attained in‘stump pulling were due to the
methodical work of a crew of six men and the winch operator. Each of four
men, in rotation, placed a wiré-rope sling around a single large stump or laced
it about @ group of small ones, A fifth man hooked the winch cable to each
sling which it was ready, signaled the winch operator to pull, and unhooked
the winch. cable’ from the sling after. the pull was completed. After each pull,
the sixth man unreeled the winch cable the 10 or 15 feet required for a now
hook-up. In a few instances, trench lines were extended for short distances
by pulling the treos without cutting them, but this method was both more
costly and more dangerous than the normal procedure. Removing timber and
font from the trench sites required 1,269 man-hours of labor at a cost of

795-13. Se :

After the timber and stumps had been removed, the trench sites were
cleared of top soil and unconsolidated overburden by a D4 caterpillar bull-
dozer, the only machine available for hire. Bulldozing began on September 6
and was completed on September 18. A total of 4,339 cubic yards of material

3047 -T-


RI. 4512

it is reached by an excellent secondary road that is wide enough for auto-
mobiles to pass, even on the steep grades on the north face of the moumtain,
Normally only 30 to 35 minutos are required to reach the deposit by auto-
mobile from Casper. Figure 1 shows the location of the deposit with reference
to Casper and the road by which it is reached. The north escarpment of the
mountain is steep, whereas the south slope ig gently rolling country inter-
sected by shallow valleys. The surface.of the deposit slopes with an average
grade of 5 to 6 percent toward Elihorn Creek, which flows along the southeast
side of tho doposit. Here, at ite headwaters, this stream is so narrow that
one can step across it, and its flow is hardly large enough to supply the
water required for diamond drilling. The deposit is covered'with a heavy
growth of lodgepole and jack pines and by an overburden of soil and hardpan
up to 12 feet in depth. The few outcrops are-of minor extent.

"DESCRIPTION OF ‘THE DEPOSITS

Figure 2 shows the areal geology of the deposit and the adjacent country.
The chromite-bearing rock is an actinolite-talc-chlorito schist that occurs
in @ series of lenses, consisting of two larger and several smaller ones,
that extend along the summit of Casper Mountain for about a mile in a general
N. 60° B, direction. These lenses form part of a pre-Cambrian complex, ex-
posed locally, which is composed principally of granite and granitic pegmatite
but contains minor areas of motadiorite, quartz-mica schist, amphibolite, and
the chromite-bearing schist already mentioned. Apparently the schists are the
oldest of these rocks and have been intruded (1) by the metadiorite and (2)
by the granite. However, the rolationship of these rocks has not been
definitely established, The pre-Cambrian complex is overlain, by Paleozoic
sediments, and the whole has been olevated by faulting 2,500 to 3,000 feet
above oxposureg of Cretaceous rocks along the northern base of the mountain.
R H. Bookwithl/ describes the general geology as follows:

Casper Mountain is a strongly unsymmetric westward-trending
anticline, of Paleozoic beds with a gently dipping south flank
and @ steeply dipping north flank, At the north of the mountain
pre-Cambrian and Paleozoic rocks lie on Upper Cretaceous beds
along a southward-dipping thrust fault. .

It is thoughtlikely that the chromite-bearing schist lenses are roof pen-
dants. -The main schist lens is about 2,500 feet long, 500 feet in maximm
width, and has an area.of approximately 15.6.acres. About 400 fect east of
it is another lens 750 feet long, 350 feet in maximum width, and having an
area of about 3.7 acres. The larger lens is essentially a tabular body dipping
about 75° to 80° northwest. .It is bordered on the south and. partly on the
north by 8 modium coarse-grained pink granite composed of quartz, microcline,
plagioclaze, and very minor quantities of biotite or other dark minerals. In
places the granite has developed pegmtitic facies. Along the reminder of
its north side the lend is bordered by quartz-mica schist, amphibolite, and
metadiorito.

7 Beckwith, R. H., Asbestos and Chromite Deposits of Wyoming: Geol. Survey
of Wyoming, Bull. 29, 1939, p. 823.

3047 “23


ae

aaa ae

spss

vou

Sample Section through Trench 2W

Sample Section through Trench 3W

gop re B Tse RTO HE
ssev ano gqecscmt Herts Lev. 9080 ees — “,
= i pce ceste ee :
err
| prough a
‘Somple Section through Trench 4W Sample Section Trench 5W
gente setete ted
ee pS ILE. 8080, ey 8080 mae 2hoete) potetrnrs tot _
= yapeea ere epee nesecteds
4 ; | : : :
ol a ‘Sample Section through Trench 7W
‘Sample Section through Trench 6W
reeesiet SE
sare
estv ocmo o
eee 00
SOLE oF Feer

Somple Section through Trench 8W

‘Sample Section through Trench 9W

Figure 8. - Sections through trenches

IW to 9W, showing locations of samples.


R. 1. 4512 Aucust 1949

UNITED STATES
DEPARTMENT OF THE INTERIOR

J. A. Kruc, SecrETARY

BUREAU OF MINES
James Boyp, Director

BERLAD OF MINES

REPORT OF INVESTIGATIONS SEP 26 1

xCH
iON

G DAVE

INVESTIGATION OF CASPER MOUNTAIN CHROMITE
DEPOSITS, NATRONA COUNTY, WYO.

“metadc38519
BY

F, W. HORTON AND PAUL T. ALLSMAN


Rt. 512

Footage Interval, Core recovery Weight, grams
‘rom ‘Oo _ feet Thches Percent Core Sindee Description

478 481 3 36 100 908 Talc-actinolite schist,
481 486 5 60 100 «1,532 do,

486 489 3 36 100 912 do,

489 495 6 61 85 1,545 do,

495 499 4 43 90 1,030 do,

499 504 5 60 100 1,403 do,

504 509.5 5.5 46 70 1,035 do,
509,5 S14 5.5 42 78 983 do,

514 519.5 5,5 38 58 812 do,
$19.5 521.5 2 13 54 218 do,
521.5 527.5 6 15 ral 287 do,
527.5 533 5,5 57 87 «1,211 do,

533 538 5 60 100 1,260 do,

538 544 6 13 18 130 do,

544 549.5 5.5 a7 41 485 do,
549.5 553 3.5 18 43 415 do.

553 555 2 22 92 430 White quartz

(pegmatite).
- 6-




Figure 3. - Small lens or pods
of chromite in trench.


RoI, WH12

—Yootage Interval, Core recovery Weight, grams Footage Interval, Core recovery Weight, grams
Fim "S fect” Tachos Percent Core stadse Description fect’ Tachos Pereeet Core “Sindee Description
222 225 3 30 83615. 666 Talc-actinclite schist, 473° «479 6 66 92 1,110 Tale-actinolite schist,
225 227 2 24 = 100 62. 331 do, 479 484.5 5.5 16 24287
227 229,58 2.5 «18 60 336 600 do. 484.5 490 55 RR 33 «ATE
229,5 235 5.5 60 91 1,521 1,679 do, 490 496 6 62 86 1,438
235 240 5 58 ” 1,421 236 do, 496 502 6 ST 79 1,270
240 © 245 5 87 95 1,380 442 do, 502 508 6 60 83 1,512
245 250 5 30 50 589 a9 do. 508 514 6 64 89 1,500
250 255 5 54 90 1,270 1,679 do, 514520 6 65 87 1,500
255 260 5 37 95 1,390 757 do. 520 525 5 6 100 1,566
260 265 5 37 62748 738 do. S25 527.5 2.5 30 100830
265 270.5 5.5 61 95 1,397 do. 827.5 531,5 4 48 100 1,061
270,58 273 25 30 100 685 do, 51.5 535.5 4 n 23° "230
273278 5 52 86 1,164 do, 535.5 537 15° 17 95 (583
278 283 5 46 77-999 do. 537542. 5 60 100 1,450
283 289 6 “4 sl (945 do. 5420547 5 60 100-1, 341
229 0-294 5 6 1019 do, S47 552 5 60 100-1, 620
294 300 6 63 85 (1,433 do, 582 557.5 4,5 94 «1,715
500-306 6 58 80 1,512 do. 557.5 565 5.5 20 301,586
306 511,555 GL. 93 1,570 do, 563568. 5 60 100-1, 646
511.5 517 5.5 87 87 1,463, do, 568-573 5 60 100-1, 642
7 Bee 5 56 94 1,427 do. 573 878,555 9 14183
BR2 BRT 5 47 78 1,190 do. 578,5 580,52 R 50 (188
327 5 60 100 1,610 do, 580.5 585.5 5 6  100-1,575
332-337 5 60 100 1,368 do. 585.5 590.5 5 6 100 1,618
337-343 6 65 @8 1,360 do. 590,5 596 5.5 25 38 610
345A 5 60 100 -1,350 do, 596 601 5 56 94 1,227
B46 355.5 5.5 6B 96 1,595 do, 60l 606. 5 54 90 1,146
353.5 359 5.5 (65 99 1,633 do, 606 «12 6 ez 86 1,395
359564 5 6 100-1, 617 do, @i2 617.5 5.5 64 97 1,565 do.
364369 5 60 100 1,350 do. 617.5 620 25 28 93592 From 617-1/2 to 645 tale-
569375 6 62 86 1,325 do, actinolite schist with
575 380 5 58 89 1,172 do. vermiculite and narrow
380-386 6 58 74 (1,495 do, bands of quarts,
386 592 6 6L 85 (1,655 do. 620 625, 3 36 100836 do,
382598 6 64 89 1,370 do. 623 629 6 53 74 (1,187 do,
398 405 5 58 a7 1,288 do, 629635 6 63 87 1,411 do,
403 408 5 37 62 31 do, 635 «640 5 35 55 747 do,
408 413.5 5.5 45 68 «61,049 do, 640 646 6 34 47 705 Granite pegmatite,
413.5 419 5, 62 94 1,270 do.
419 3 36 75 "703 do, Hole 7 Bearing: S, 50° E,
425 428 56 93 1,218 do. Iocation: 340 N., 150 E, Dip: 50°
428 454 62 86 1,536 do, Elevation at collar: 8,047 feet Depth: 844 feet,
434440 65 es 1,463 do,
440 446 63 eg (1,541 do, 0 B8 Soil and broken weather—
446 «451 60 100 1,475 do. ed rock (quartz-mica
451 457 52 72 «1,311 do, schist (?),
457 462 60 100-1, 560 do, e287 5 36 60 «779 Quartz-mica schist,
462 467.5 62 94 1,270 do, broken but solid,
467.5 473 33 50 401 do, a7 93 6 28 39 505 586 do.
93 100 7 No core do.
100-105 5 25 42 446 1,882 do,
3047

= 22-


RI. 4512

obtained was 581.5 feet. This distance, subtracted from the total length of

the holes, leaves 3,041.5 feet as the total length of possible core, based

on which. the average core recovery was 62.6 percent. This rather low recovery
wes duo mainly to drilling through bands of vermiculite and soft, friable
schists from which little if any core could be obtained. It was noted, however,
from examination of both cores and sludges that where any reasonable amount of
chromite was present the core was reasonably strong and usually gave good re-
covery. Hence, the core samples are believed to represent such sections

fairly, although where partial cores were obtained they are not, of course,
truly representative of the entire section drilled. —

In general, all core samples consisted of @ longitudinally split half of
all the core raised by each pulling of a 5-1/2-foot core barrel. In all, 631
core samples were taken, but only 139 were split for analysis. . The position
and analyses of these samples are given in appendix B.

Sludge samples were taken over the same intervals as the core samples
so that the analyses of core and sludge might be properly combined to give a
weightod analysis that would represent the interval drilled.

All sludge from holes 1 to 5 was saved, dried, and weighed, as well as
that from the upper parts of holes 6, 7, and 8. However, before completing
the lattor holes it became evident that the sludge samples ag a whole were
of little value because of caving of the holes along the streaks of vermiculite
and soft schist frequently intercalated in the schist lens. In many instances,
the sludge was so diluted with caved material that it was valueless as a
sample, and as amplo core was being obtained to give a true picture of the
chromite content of the richer streaks of schist, it was deemed a waste of
money to collect further sludge samples. .

In all, 304 sludge samples wore collected and weighed, but only a
selected few of them were analyzed to. determine if, as concluded from panning
tests, the sludges in general contained mch less chromite than the cores.
Five sludge sémples containing 0.05 to 10.7 percent Crj0z were compared with
corresponding cores, and every core was found to be conatderably the richer.
Details of this comparison are shown in table 2.

TABLE 2. - Comparison of analyses from diamond-drill
core and sludge semplos

; ° 1 Weighted
Core Sludge Length |Length |Percent | Percent janalysis,
Sample |Percent |Sample |Percent|drilled,| core, |core by jsludge by| percent
Drill | No. Cro05_| No. Crpe03 |inchos | inches |volume | volume Cred,
Bo... | DO | “6.14 [DST 0.05 | 36 in 3.95 | 96.05 0.29

DLO 4.51 | DS2 1150 72 64 | 31.56 | 68.44 2.45

Die 5.12 | Ds3 3.10 | 66 53 | 28.51 | 71.49 3.68
E3 | 12.50 | ESL 5.55 | 60 20 | 11.84 | 88.16 6.37
E2__| 16.00 | Ese 10.70 | 2h 10 14.79 | 85.21 12.48

3047 -10-




RI, 4512

until shipped. Snowstorms interferred with trench sampling on October 9, 10,
and 26,-but it was completed on.Octeber 31, In all, 694, samples: with a total
weight of approximately 32 tons were cut.from 6,222 feet of. channel in the
trenches and shipped to Reno for analysis. Longitudinal sections of ‘each
trench showing the position, interval, and number of each sample are shown in
profile on figures. 6 to 9 and in the plan on figure 5.

The only. sampling done .on the second largest: schist. lens, which lies
about 300 feet east of the min lens, was.on.the, north wall of a road cut
where the chromite-bearing schist was exposed for a length-of 90 feet. Here
& continuous channel was cut over the entire distance. and, divided into 15
individual samples, each representing an interval of 6 feet. The position of
this cut and of the os) individual samples is shown. on figure 10.

Diamond Drilling
Data regarding Siemon drilling are. summarized in table 1.
TABLE 1. - Summary of dtemond-drill date

HLevation
at Depth | Core
ae collar, | Dip, on dip,| size, Lo

Hola .__ Location ft. degrees|Bearing| feet in, | Started Completed
115.50 W., 1.90 N. | 6,007.0 20, [8.300 [ihe "7/8 [Sept.13 Abandoned
: Sept, 21

215.50 W,, 2.60 N.| 8,072.5 | 40 | do...| 583 | dos '|Sept.23 Oct. 25
3) 7.00 W., 1.30.N. |.8,067.3 20 do. 85 | do. .| Sept. 24. Abandoned
cob iy oe, . . 4 =, Sept. 18

4 | 7.00 W., 1.30 N. | 8,067.3 ko do. 389. | do. 4Sept.19. Oct. 5.

5 | 9.50 W., 2.00 N. | 8,081.6 ho do. 379 | do. |Oct, 6 Oct. 23

6 | 2.75 N., 2.00.W. | 8,061.8 50 do. 646 | do. | Oct, "26 Nov. 13

7,135.40 N.,, 1.50.B. | 8,047.0 50 | do. Buy | do. [Oot. 25 Dec. 3

812.50 N., 5.00 8. | 8,012.5 | . 50 do, 555._| do. |Oct..28 Nov. 18

The total footage drilled was 3,623, The positions.of the various drill
holes are shown on figure 5. Sampling maps and geologic. profiles of the ‘2
individual holes are given on figure 10.

Diamond drilling proved (1) thatthesubsurf'dce schist ia of the same
general character as and hag & comparable’ chromite content to that on the sur-
fades+{2). that ‘the schist extendy,“at-least’in séveral placos,‘to vertical
depths’ of 400..and 500 feet;.and (3) that with depth. the intrusions of granite,

pegmatite, and metadiorite increase both in frequency and width,’ bearing out
the; gupposition that the schist lens is a roof pendant and indicating that it
may terminate within: “a few hundred foot: ‘beyond the maximim ‘depth: reached by
drilling. -

‘A total of 1,903. 5 feet of core was recovered from 3,623 feet in the eight
diambni-drill holes. Howaver, the total distance, from -the collars of the holes
through: overburden and-unéonsolidated material to’ where ‘cores were first:

3047 “9






Rel. W512

‘APPENDIX B
Sample Depth, fect Interval, Percent Sample Depth, feet Interval, Percent
Analyses of Diamond Drill Core Samples No, From To feet Gre05 No, From To feet" _Ora03_
Sample Depth, feet Interval, Percent Sauple Depth, Te eet Interval, Percent > Percent Hole 4 Hole 5
“Noe Fee Te feet Grg0, _No, From fo feet" CrgOa a
R88 8S 3 0,55 cl 159 164 5 0,46
Hole. 1 D25 421 426 5 R39 46 7 +50 cz 164 170 6 205
D26 426 «451 5 BR 12) 126,50 5,5 230 cs 170 «176 6 226
ax 75077 2 De? 451 436,555 Ba 126,5 131 4.5 o15 ca 176 162 6 105
a2 77 «79 2 D2 436.5 442 5.5 BS isl 1s 5 226 C5 162 186 4 215
43007921 3 D29 442448 6 BE 193 199 6 31 cé 198 208 5 205
a4 Bl 8S 2 DIO 448 «455 5 B7 199 204 5 C7 «203 «202.5 © 6,5 105
A583 8B 9 Dsl 453458 5 BE 204 209 5 cs 22 218 6
a6 9298 2 Dsz 458462 4 B9 209 214 5 co «218 225 5
7 948 4 DSS «462467 5 Mo 214 219 5 clo 223 «(228 5
48 98100 2 D34 467472 5 Fl 219 228 4 Cll «356 «364 8
Ag 100 105 5 . D3s 472477 5 MZ 223 228 5 clz 364 369 5
Alo 105 110.5 = 55 1.89 D6 477482 5 B13 228 229 1 cls 369 «376 7
Al o,s 116 5.5 420 «DBT 482487 5 Fl4 294-298 4
a2 i6 ue 8 236 «3B 487 492 5 RIS 298 302 4 Hole 6
As 119 1255 65 1.48 D9 492 496,545 BIG 302 306 4 127 1a 4 14,00
Ala 125.5 131 5.5 1.17 D4O 496.3 5OL.B = 5,5 M7 306 «312.4064 ER 1sl 133 2 16,00
M5 1s] 185 4 1.85 -D4l_-«-S01,8 507.5 5,7 Bis 315 318 5 E3145 148 5 12,50
42 -§07,.5 515 5.5 Big 316 524 6 E4 472 473 1 9.45
‘MCore from 75,5-76 was granite and D430 «513.518 s B20 824 529.5 5,5. ES 479 484.5 5,5 10,70
was excluded from the sample, D4 «S18 525 5 Bel 829,5 384,55 B6 521,5 523 15 11,25
D&S 523-525 2 Fe2 854,5 340 5.5 E7 849 550 1 15,40
Bole 2 Da6 525550 5 B23 340 4 Eg 552 554 2 17,80
D47 «580-582 2 Re B44 349 5 EQ 557.5 558.5 9 1 7,00
DL 153 155 2 1.84 Das 532 538 6 Be5 349854 5 B1O  562,5 563.5 1 8,65
D2 155 160 5 26l = -D49 3B SHZZ 4 R26 554557 3 El 613 614 1 19,95
DS 165 170 5 *72 “DSO $42.2 846.7 4.5 Re7 357-359 2
D4 266 2695 © 5.5 +46 = «DSL 546.7 551,8 95.1 Ree 559 564 5 Hole 7
DS 269, 5 274 4.7 46 D52 -5551,8 557.3 5.5 B29 364-369 5
Dé 274 279 5 +46 (DSS «557,3 563 5.7 B30 569-374 5 Gl 233 240 7 1,95
D7 «27928, 21 +26 «DSA 5635685 SS. Bal 374377 3 G2 $22 B25, 3 4,85
De 281.1 288 1.9 -41 «DSS 568,5 5715 5 BS2 377381 4 C3 546348. 2 5.65
D9 283 286 3 DS6 S71,5 575 15 B53 SQL 885.25 2,25 G4 367-373, 6 1,15
DIO 286 292 6 Ds7 «875 «878 5 B54 385.25884,75 1,5 G5 382 B84 2 2,45
DIL 292 297.5 55 G6 397.5 404 6.5 1,00
Dlg 297.5 303 5.5 Hole 3
Dls 503 306 3 Hole 8
D4 506 sll 5 Abandoned at a depth of 85 feet
DIS sll 316 5 ~58 before any regular core was obtained. Fl 392.5 395 2.5 5.20
pls 516 sal 5 272 F2 397398 1 2,40
DIT 321 BRS 2 +05 F3° 467 472 5 2,55
DIG 590.5 592 1.5 205
Dlg 392 397 5 “77
p20 397 402 5 272
D2l 403 406 3 +97
p22 406 «(411 5 282
pes 41 416 5 “77
Dea 416 «421 5 1,02

3047 -Uue-


RI. W512

Hole 1

Location: 550 W,, 190 N,
Elevation at collar:

8,067.6

APPENDIX C

Diamond Drill Hole Logs

Bearing: S, 30° E,

Dip: 20°

Depth: 142 feet (abandoned)

eo Tntervel, Core recovery Weight, gran:

Inches Percent Core snage

Description

To__ feet
o SL Sl
Sl 55 4
5575 20
77 2
7 «79 2
79° Bl 2
Bl 83 2
83 2 9
92 (94 2
4 98 4
98 100 2
100 105 5
105 lo, 5,5
llo,s 116 5,5
ne ne 4
ne 125.5 6.5
125.5 131 5.5
131135 4
135-142 7
Hole 2

24

Location: 5.50 W., 2,60 N,

Elevation at collar: 8,072.5

0 68,5
68,5 70,
70.5 74
am 9
97 102
102 107
107, “az
ne 17
n7 neg
nig 122
122 127
127 182
3047

68,5

°

19
BR

0
23
36
18
18

3
u
Ra

0

50

100

°

o8SESS 85088

Sludge
was not
weighed
as it
None was not
1,300 repre-
‘700 setnative
880 and the

660 hole was
710 abandoned

Soil and broken rock,
Broken pegnatite and
green actinolite
schist,

75-1355 normal actin-
olite schist with
chromite in large
greins and small
knots up to 1/2~in,
in diameter, From
76-77, pink pegna~
tite consisting of
quartz and
ortheclase.

Bearing: S, 30° E,

Depth: 588 feet

330
650
480
480
410
120
210
380
880
550
None
Dip: 40°

0 °

? 0

? °

o 0

425 510

652 1,850

360 1,785

327 (14060

263 1,118

260 1,456

0 1,260

Overburden and badly
weathered quartz—
mica schist,
Quartz-mica schist.

do.
Unconsolidated,
Quartz-mica schist,
From 106 metadiorite,
Metadiorite,

do,

do,

do,
One foot dark schist.

Footage Interval, Core recovery Weight, grams

From To feet. Thches Percent Core sludge Description

ise 138 6 28 39 = 480-«-2,814 ‘To 133 vermiculite
granite-pegm tite,

138-143 5 al 52 630-2, 840 do,

430 (145 2 13 54 «185710 do,

45047 2 6 25 65 370 do,

147,150 3 29 81 656. «= 280 From 148,5 fine black
schist.

150-155 5 a4 57 718 «= 655.“ Fine black schist,

185 160 5 14 23 = 280-630 From 153 talc~actino-
lite schist with
chromite,

160-165 5 ) ° 0 2,749

165 170 5 36 60 792 19,119 Fine dark green schist.

170-178: 5 aL 35 «405-6825 Vermiculite to 173.55
quartz 173.5 to 174
thermetadiorite,

17s 178 3 26 72 618 2,340 Metadiorite.

178185 5 57 95 1,553 6,087 do,

183168 5 31 52 806-6, 822 do,

188-193 5 se 98 1,608 8,440 do.

193-198 5 60 100 1,581 8,100 do,

198 203 Ss 50 83 61,258 8,435 do.

203-208 5 60 100 1,380 15,872 do,

208-218 5 9 15 "160 8,910 do.

213218 5 60 100 1,500 8,941 do,

218-223 5 60 100 1,410 4,250 do,

223-228 5 35 59 760-2, 853 do,

228 232 4 20 42 397 1,420 do.

232238 6 60 83 375-2, 960 do,

238 243 5 60 100 -1,467 3,900 do,

2430248 5 50 83 (1,314 2,081 do.

248 255 5 60 = 100-:1,636 8,459 do,

253258 5 60 100 1,710 2,210 do,

288 263 5 60 100 -1,843 5,475 do,

263 «269 6 56 94 1,625 2,990 From 266 gray-green tale-
actinolite schist with
chromite,

269-274 5 45 75° 1,382 1,859 do,

274 «(279 5 49 e2 1,250 1,216 do,

279° 28L 2 18 75 320-1, 319 do,

281 283 2 aL e8 414.880 do,

285-286 3 4 n 56 1,503 do,

286 292 6 64 89 1,520 = 715 do,

292 297.5 5.5 BR 49 “691685 do.

297,5 303 5.5 53 el 1,346 210 do.

303 506 3 a1 5B S16 823 do.

306 sll 5 a 69 984 440 do,

Sil 316 5 38 65 830640 do,

B16 32h 5 60 100 1,387 1,240 do,

321326 5 26 43 462 1,770 Granite-pegmatite

3260 381 5 54 901,218 do,




R.I. 4512
APPENDIXES
A. Analyses of trench samplos.....essseecccevcesscvescssees 13

B. Analyses of diamond-drill core samples....
C. Diamond-drill hole Logs...cccccsccccscccescccerecssecees§ 19

INTRODUCTION AND SUMMARY

Investigation of an extensive deposit of chromite-bearing actinolite-talc
schist situated on the summit of Casper Mountain, 10 miles south of Casper,
Wyo., was one of the first projects undertaken by the Bureau of Mines under
the Strategic Materials Act (Public 117, 76th Cong., Ch. 190, 1st sess.), for
which an appropriation became available August 9, 1939. During the previous
summer, the Geological Survey made a magnetometrical survey of the area in
which the schist occurred. It was exposed in several small lenses and two
larger ones aggregating about 19: acres in area. Although the occurrence of
chromite here had been mown for many years, the only work done on the deposit
was the digging of a few shallow pits on some of the more promising outcrops.

From August 23 to December 3, 1939, the Bureau of Mines investigated the
larger of the two main schist bodies. Twenty-four trenches having a total
length of 8,073 feet were dug across the deposit, and its subsurface extension
was explored by 3,623 feet of diamond drilling. Over 32 tons of samples were
shipped to the Metallurgical Division of the Bureau of Mines at Reno, Nev., for
reduction, analysos, and ore testing, In all, there were 853 individual
samples. Geological maps, based upon examination of outcrops, trenches, and
drill cores, as woll as a contour mp of the arca were made by the Geological
Survey.

ACKNOWLEDGMENTS

This report was prepared for publication by the Mining Division, Lowell
B. Moon, chief, under the supervision of Paul T. Allsmen, chief, Salt Lake
City Branch. The project work was done by the late F. W, Horton, mining
engineer, under the supervision of the late Chas. F. Jackson, former chief of
the Mining Division, and E. D. Gardner, supervising engineer of the Southwest
Experiment Station,-at. the time the work was done.

The project engineer acknowledges the assistance of R. R. Trengove, mining
engineer, who spent a month organizing and supervising diamond drilling, and
Kirk Stephenson, of Princeton University, and E. L. Stephenson, geologist for
the Geological Survey, who conducted the magnetometrical survey, prepared maps
of the arca, and logged the cores.

LOCATION AND PHYSICAL FEATURES
The Casper Mountain chromito deposit is situated 10 miles by road south
of Casper, Wyo., just over the crest of Casper Mountain, on its southern
slope, in secs. 16, 17, and 20, T. 32 N., R. 79 W., 6th P.M, Its altitude
is about 8,000 feet, or 3,000 feet higher than the city of Casper, from which

30h7 -2-


BI. W512

Hole 8 Bearings 8, 30° E,
Location: 275 N., 5 By 50°
Elevation at collar: 8,012,5 Depths 555 feet

Footage“ Tnterval, Fecovery Weight, grams
Fee ae tee eer eee Cone ears ge

Description

0 83 83 ° 9

83 99 16 oO °

99 104,555 9 13 162 969
04,5 110 5.5 8 12 161 «2,381
po 16 6 45 63 a76 1,518,
1612 5 52 87 «1,078 458
11-126 5 82 53 645 204
1g6 0 lal 5 n 18 210 2,284
isl 156 5 25 ae 497 1,900
1360 141 5 8 18 140 1,810
141-146 5 3 5 49 2,765
146148 2 7 19 130° (1,615
148150 2 5 a 67 821
150-154 4 10 au 208 736
154 «158,50 4,5 28 52 527 1,786
158,5 163.5 5 33 55 637

163,5 167 3.5 al 14 567
167-172 5 53 89 1,258

17 «175 3 25 70 545
175180 5 13 a2 226

180 (187 7 “ 52 728
187-193 6 42 59 792
193-199 6 SL 7a 934
199-202 3 33 92 664

202 207 5 55 92 1,446
207-218 6 36 50 775
2130217 4 a 65 592

217 ah 4 9 19 173
221-226 5 30 50 539

2260 al 5 al 35 376

231 233 2 5 al 7
235237 4 24 50 428
237-248 6 59 82 1,260

243 248 5 60 717

248 254 6 32 45 590

254 260 6 29 40 531

260 265.5 5,5 65 96 1,250

265.5 271 5.5 ae 28 445

R71 276 5 28 a7 528

276 281 5 ere 87 660

zal 285 4 21 “4 295

285 287 2 16 67 290

287 292 5 22 37 396
292-295 3 27 ot 410

295 299 4 48 100 os

Soil and weathered rock,
Granite pegmatite
do

do,
do,

do,
Dark green, fine schist,

‘do.
black rock (basic
dike},

Very dark green, fine
schist,

do.

do,

do,

do.
Granite pegnatite,
do.
do.
do,
do,
do,

=e

~Foota: Interval, (ore “Fecovery Weight, grams
Fron "15 _"teot _” Inches Percent Core —“Stadge Description
504 5 60 100 as Granite peematite,
509 5 58 96 1,188
514 5 60 100 1,462 From 508, to 529, dark
gray schist, highly
silicified,
a4 518,545 28 4300 454 do,
318.5 523.5 5 au 35 B71. do.
323.5 526 25 30 100 487 do,
326 381 5 45 75 859 do,
331536 5 40 66 829 Pegnatite
3363415 5518 33 552 do,
31,5 347 5.5 33 50758 do,
347 B52 5 28 47 491 do,
82358 6 66 92 1,294 do,
BSB B62 4 33 69 675 Variable, silicified
schist.
362 565 3 31 86 528 do.
365368 3 23 64435 do.
568 B71. 3 36 «100780 do,
S71 375 4 38 79 (778 do,
375380 5 60 = 100--1,590 Fron 372 to 391,
netadiorite,
380385 5 60 = 100 -:1,470 do,
385 391 6 40 86819 do,
B91 5965 5,5 55 85 1,300 Tale-actinolite schist
(best chromite appar—
ently from 397 to 398,
466 to 472 ft),
396.5 402 5.5 53 80 (1,248 do,
402 407 5 42 70 “ols do,
407 411 4 48 100 (1,177 do,
aul 414 3 8 22189 do,
44 418 4 22 46 427 do,
aia 421 3 ae 33247 dow
421 426 5 6 100 1,290 do,
426 431 5 ° ° do.
451 436 5 a7 45 (589 do,
456 441 5 ° ° do.
441445 2 7 290048 do.
445446 3 5 u 80 do,
446 447.5 1,5 3 16 36 do,
447.5 451 35 42 100 1,012 do,
451 456 5 60 100 1,440 do,
486 460 4 a7 98 1,067 do,
460 463 3 26 72 592 do,
463 468,555 62 94 (1,317 do.
468.5 474 5.5 44 67 992 do,
47478 4 36 75 (872 do,


Rel. W512

‘Footage Tnterval, Core recovery Weight, grans Footage Interval, Core recovery eight, grams
Fron" feet” Tnohas Feresnt ae Description Fron "te tect” Inches Percent tore sass Description

105 6 5 7 87 1,899 Quartz-mica schist, 306.5 512 5&5 40 80 B29 Tale-actinolite schist
broken but solid, with chromite,
mor 6 48 67 = 857-2, 562 do, 312-16 4 32 67 680 do.
u7(1ee 5 50 50 610. 2,049 do, B16 321,555 50, 4688S do,
ze 127 5 45 75 878 4,258 From 122 to 142, fine 321.5 526.5 5 44 74 840 :
green to black schist, 326.5 335 6.5 No core
W7 182,555 88 59 767 2,600 do, 333359 6 10 lol do,
182.5 158.5 6 66 92 550 1,821 do, 339345 6 31 43° 652 do.
138,5 144 55 47 n 80 2,355 From 142 to 160, granite S351 6 66 91 1,410 do.
pegmatite, variable, 351557 6 No core
144 48 4 38 79 694 1,452 do. 357-36 4 wv 3S 295 do.
148151 3 13 36192425, do, 36l «566 5 4. 78 973 do.
isl 156 5 40 67 = -723.«1,264 do, 3660871 5 59 98 1,175 do.
186 158,525 (17 56 273728 do, 378765 545 60 ol 1,446 do.
158,5 164 5.5 41 62 868. do, 376.5 361.5 5 15 25 “289 do,
164165 1 No core 3EL.5 384.5 5 35 97 = 780 do.
165 170 5 56 17 RAL do, 384.5 390 5.5 33 460718 do,
170-175 5 29 49 S8L do, 390 392 2 24 100 595 do,
175180 5 38 55639 do, 392««397.5 «S45 40 60 8-886. do,
iso 182 2 28 97 895 Granite pegmatite, 397.5 403 5.5 59 89 1,370 do,
variable, 403 408 5 60 100 1,494 do.
1s2 187 5 25 42 570 do. 408413 5 4 23 263 do,
187-191 4 43 89 (938 do. a5 418 5 52 86 1,139 do,
1 196 5 40 67842 do. 418 423.5 5,5 36 55688 do,
196 © 201 5 48 80 (1,025 do, 423.5 427 BS 8S 79 «640 do,
201 206 5 44 73 865 do, 427 452.5 5,5 62 94 1,536 doe
206 «208.5 2.5 30 100 691 do, 452.5 437 4.5 54 100 1,490 do,
208.5 215 4.5 19 35 «806 do, 437442 5 52 87 1,462 do,
213217 4 15 BL 263 do. 442 446 4 29 60 do.
217-223 6 n 15 190 do. 4460447 1 29 92 do,
223-228 5 50 84 (978 do. 447448 1 8 67 do,
228-253 5 No core 448 © 450 2 No core
2330284 1 9 75 100 Talc-actinolite schist 450 456 6 12 aw From 450 to 480-1/2,
with chromite (best pegmatite.
chromite 322 to 325, 456 462 6 55 7 do,
567 to 373, 382 to 564, 462 467.5 5.5 44 671,555 do,
397-1/2 to 404), 467.5 473 5.5 42 64 do,
234-240 6 34 47-207 dc. 473479 6 45 631,298
240 247 7 16 19 (340 do, 479 484.5 5,5 55 83-280 From 4801/2 to 489,
247 252.5 5,5 No core black basic dike, hard,
252.5 26 1.5 lL 1 150 do. dense.
264 «267 3 a 5B 242 do, 484.5 490 5.5 30 46 (388 do,
267274 7 33 3900555 do. 490 492 2 No core
274 © 280 6 23 32 Bal do, 492 496 5.5 Re 57 Pegnatite,
280 285 5 wv 28 384 do, 496 500.5 4.5 12 25 .
285 © 290 5 54 90 1,107 do, 500.5 501.5 1 12 100-300 do,
290 295 5 55 92 1,270 do, 501.5 503 1s 15 500 171 do.
295 304 9 4 13 ae do, 505 505 2 24 100 497 Black, basic dike, hard,
304 «806,525 No core dense,
= 23-


% S

Wa
7 PSS eS
Na A NUON ND)
RA STN
—— ene vie .s VAY AI ea
ARORA REE 0
wef N) NWO SRE ma
ol) LS SEAR —
PSN oe ll
CARTE LR ”
Zn G << i x er Ni
of KES wal WX 8 nome Scmsr ouT.MED BY 7
\y XY Ny RO i a 560 _
RS RN ¥
MANNUNNNN SS ate ~
REE REIN SE
XX)
eR INSEE
ZIRE
AN \ (As
KV) A 8
oP // YE iy
/ PILL [hi AE
SCALE OF MILES

Figure 4. - Contour map showing relation of trenches and diamond drill holes to magnetometer survey.


aR 7K 2 oe | a a
1 .
fi
pat {| ow
a — an
4 a!
$F
f
ln | on

1
ra |
4 a
I
| compen | pessseee-ar grad SAL.
os i eae He ‘
a ne es oe 7] \ La "\
f Jaomees 94: 2 ~ ag jaa
NJ se Ree aR > . -

zZ :
ul
| | uf

Figure 5. - Plan showing locations of trenches and diamond drill holes.



R. I. 4512,
August 1949,

REPORT OF INVESTIGATIONS

UNITED STATES DEPARTMENT OF THE INTERIOR - BUREAU OF MINES

INVESTIGATION OF CASPER MOUNTALN CHROMITE DEPOSITS
NATRONA COUNTY, Wy0.2/

By F. W.-Horton2/ ena Poul 7. alignan?/

CONTENTS

Introduction and SuMmMAaryrccercccvcecccevancheceenaseevevsnse

+ Acknowledgments... reeccevescseves
" Location and physical features......
Description of the deposits.......
MINCLALOZY ececcvecserssurevesneene
Work: by the Bureau of Mines....
Trenching.ssscevsrseceee
Trench sampling...
Diamond. drilling...
Results of investigation. ...ssssceres

:
ty

a :

Po Oa funn mfg

ILLUSTRATIONS

-Follows
Fig. __Bego
1 Index map showing location of Casper Mountain
chromite, deposits, Natrona County, Wyo. essccscerece
Map of areal geology, Casper Mountain chromite
GOPOSLtS. crccvccevvceeversveneesseeraesevesessvessee
Small lens or pod of chromite in trench... ..seecoederae
Contour map showing relation of trenches and diamond-
drill holes to magnetometer SULVOY..eresveceecteeeee
Plan showing locations of trenches and diamond-drill
HOLES eccseccereececevercveesrecvevecessesssecensens
Sections through trenches showing location of
BAMPLOBs seecscesardeceeasecssvccaececeseveneennerees
10 Sample sections of drill: holes 1 to 8 and road
GAMPLO NAPs eeessscveweveeseveevessvecvecsesievascnes

wo VU FU DD
oo nn FVM

i/ The Bureau of Mines will welcome reprinting of this paper, provided the

* following footnote acknowledgment is made: “Reprinted from Bureau of
Mines Report of Investigations 4512."

2/ Former Mining ‘engineer, Bureau of Mines. (Deceased. )

3/ Chief, Salt Lake City Branch, Mining Division, Bureau of Mines.

30K7


RI. 4512

Sample Taterval, Percent © Sanple Tnterval, Fercont

No, Trench ___ feet Org0a No, Trench _ feet org0q

591 SE 10 0.50 64310 5 0,92 Samples from Road Cut in East Lens
592 10 44 5 16,69

593 10 645 8 156 Sample Interval, Percent
504 0 es 10 °37 Nos feet Oren
595 6 647 0 :

£98 8 3 36 er 695 6 10,92
597 ew 10 649 3 2.16 696 6 7.04
598 10 650 7 21.25 697 6 17625
599 7 651 6 6.65 698 6 8.81
600 5 652 10 <6 _ 6 5.5L
601 5 653 8 224 700 é 25k
602 5 654 10 2,59 701 6 2.08
603, 5 655 10 2.20 708 § 2.05
504 5 656 10 1,79 708 8 1615
605 5 657 10 4.64 704 6 2,08
606 5 658 10 205 705 é 11.98
607 5 659 10 142 706 6 5
608 10 660 lo 2.71 707 6 22,62
609 10 66l 7 4,91 708 6 3.94
610 10 662 3 1,79 709 6 1.38
en 1s 663 10 157

612 on 4 664 10 2109

61s 7 665 8 3.20

64 5 666 9.5 1,50

61s 5 667 1 24,90

616 5 668 95 1,00

7 7 669 3.20

618 8 670 10 2.30

619 9 671 10,5 4.40

620 6 672 uv 390

62. 7 673 10 4,20

622 lw 10 674 6 80

623 10 675 7 5,20

624 10 676 5 10,40

625 10 677 5 1,40

626 10 678 5 3.00

627 20 679 5 10,00

628 10 680 5 3.10

629 10 681 5 3.50

630 5 682 5 12,20

651 5 683 5 4,90

632 9 684 5 1,00

633 10 685 5 4,60

634 1.8 686 5 10,00

635 6 687 5 10,20

636 10 688 7 1,70

637 io 669 aw 10 327

638 low 690 5 144

639 10 691 5 6.40

640 10 692 5 1.38

eal 0 693 5 3.77

642 10 694 6 72

-16-




A Century of Conservation




RI. 4512

A section showing the location of samples in the road cut are shown on
figure 10. The analyses are given in appendix A.

Figure 10 gives the sections through diamond-drill holes and location of
samples. Analyses of diamond-drill core samples are given in appendix B, and
logs of holes are given in appendix C.

3047 -le-


BI. 12

Foota; Interval, Core recovery Weight, grams Hole 6 Bearing: S, 30° E,
Fron "tp tect.” Tnches Percent Core Err Description Iocation: 275 N., 2 W, Dip: 50°
Elevation at collar: 8,061.8 Depth: 646 fect,
182188 6 56 = 78~=—«1,320 2,585 From 186 fine, green
schist and granite Foota; Interval, Core recovery Weight, grams
interbanded, Fron" _ “feet” Tncbes Pereent_Core —“Staare Description
188 195 5 60 100 1,767 1,067 do.
193-198 5 39065 991 1,650 do, o 8 ° ° ° © Soil and weathered rock,
198-208 5 42 (70 929 1,683 Fine, dark green schist, 67 5 28 47 57 © From 67 to 103 tale~
203 «208.5 «5,5 21 382 414 1,654 Gray-green talc actin- actinolite schist,
olite schist to 209.5, little chromite,
208,5 213 4.5 46 85 1,100 1,443 Granite to 212, 72 7 5 26 44 620 1,648 do,
215 (218 5 47° 78 ~=—«:1,229 8,258 Gray-green tale actin— 7 83 6 29 40 657-—«1,570 do,
olite schist with 8388 5 43 T2595 398 do,
chromite, 8 (83 5 32 55 «670 451 do.
21s 223 5 5588 975 6,763 do, 938 5 26 44 © 843.—«1,049 do,
225-228 5 2 85 B12 7,793 do, 98 104 6 25 355761, 156 do.
228 233, 5 6 100 1,121 6,449 Metadiorite, 104-109 5 30 50  682.««-2,813 From 103 to 117, pegma~
235-288 5 46 77 «1,025 5,555 tite and vermiculite,
238-243 5 49 82 796 1,241 ios 45 55 17 26L 8, 465 do.
243248 5 18 80 216 1,595 14,5 1195 5 45 75 1,200 2,222 do,
248 253 5 26 43 409 7,442 19,5 125 5.5 3S 55 "896 1,978 Dark green schist, some
253 257 4 18 al 294° «7,442 chromite, 117 to 121,
257 (262 5 3555 671 1,301 125 Isl 6 a4 87 1,017 4,641 ‘From 121 to 148 tale—
262 267 5 60 100 1,372 1,535 actinolite schist and
267.275 6 65 90 1,595 1,566 chromite, Best chromite
273278 5 60 100 1,970 1,180 apparently from 124 to
278-283 5 59 98 1,925 "990 124-1/2, 127 to 151,
283 «288,545,560 SL 1,848 855 181 to 133 and 145 to 148,
288,5 294 5.5 65 99 1,965 928 isl 138 2 10 42 467 2, 062 do,
294299 5 39-65 s«1,062 620 1350-138 5 8 1s 182 5,642. do.
299 504 5 60 100 1,960 2,107 138145 5 20 33 4452882 do.
304 306 2 ° © No core 1,153 1430-148 5 20 33 (1,071 = 1,973 do,
306 Bll 5 Sl 851,180 2,682 ls (154 6 5 7 58 3,582 From 148 to 164-1/2
sls 7 65 «77 «1,754 5,010 soft tale-actinolite
BIB 823 5 60 100 1,465 2,462 schist,
323-828 5 49 82 1,014 1,247 154159 8 15-1472, 966 do,
328 «383,555 50 76s, 291246 159 164,5 18 27 «2882, 769 do,
353.5 359 55 82 68 1,423 — 265 164.5 170 50 76 1,412 1,943 From 1641/2 to 185,
339344 5 “MOST 868 5,500 solid talc-actinolite
B44 349 5 60 100 1,438 4,479 schist,
349354 5 60 100 1,550 5,551 do, 170 172,525 28 7 ~~ «619 707 do,
354359 5 3863 841 2,623 Gray-green actinolite 172,58 178 5.5 5? 87 1,518 2,800 do,
schist with chromite 17812 4 46 96 1,101 981 do,
to 356, 182 186 4 56 75 "944 = (1,693 ,
359564 5 3050 490 462 do, 186191 5 47 79 1,147 1,193 Talc-actinolite schist,
364869 5 “a OS? 661 1,696 do, 19 196 5 47 "680 760 °
369572 3 13087 230 515 do, 196-201 5 60 100 1,476 2,300 do,
372376 4 “4 71 537 2,442 do. 201 © 206 5 21 35 4702466 do,
376879 3 25 «69 822 2,679 Pegmatite to 577, 206 209 3 12 33-290 1,050 do,
209-213 4 37 77 «878,181 do,
as 218 5 52 87 (1,157 1,865 do,
218 eee 4 10 al at do,


* waar or rear

Section through D. D. Hole 3.84
‘showing Location of Somples:

Eo
100 8

1a

ater i 4:

‘ a = o
ar ow fer

Section through D. D. Hole | & 2
‘showing Locotion of Sample

| te. 7700

Scat OF FEET

Section through D. D. Hole 6
‘showing Location of Samples

Figure 10. - Sample sections of drill holes and road sample map.



i RI. 4512

Many of the chromite grains show well-developed octahedral faces, and
some of thom are 1/16.inch in diameter. Analyses show that the chromite is
variab} in composition and is generally high In iron. Analyses by H. F.

Eppa on concentrates of this chromite show 46.6 percent Crp05 and 36 per-
cent FeQ in one sample and 26.6 percent Crg0z and 63 percent FoO" in another.

In both samples the total iron was calcula: as FeO. A more complete analysis
of concentrates, furnished by E. L. Stephenson of the U. S. Geological Survey,
‘Rollows!

Analysis of chromite concentrates from Casper Mountain

Percent

Wh. 7h

Magnetic measurements indicate that magnetite in varying percentages is
intimately: mixed with the chromite, rendering some of it so magnetic that it
‘can be. lifted by an ordinary hand magnet, whereas other grains are but. slightly
magnetic and require a mch stronger magnetic field to attract them. The. color
of the chromite also varies notably. Generally it is the characteristic black,
but moh of -it ranges from dark to light reddish brown.

Freedom of the schist from other minerals of comparable. specific gravity,
and the granular form of the. chromite make the latter very easy to concentrate
by ordinary gravity methods such as tabling.

WORK BY THE BUREAU OF MINES

August 17 to 22 was spent in preparing for the investigation and in obtain
ing permission to prospect from Homer T. Darlington and. Minal E. Young, the
Consolidated Mining Co., the City of Casper, the Wyoming Baptist Convention,
and Albert.N,. Zuill, all of Casper, and from Willard C. Brinton, Croton-on-
Hudson, N, ¥.,. and George H. Houston, Greenwich, Conn., all of whom held
interests in the area. covered by the deposit. The agreements with the City of
Casper and the Wyoming Baptist Convention specified’ that.all excavations on
their property were to be refillod efter sampling was comploted.

Exploration of the deposit was confined to trenching and diamond drilling
of the largest schist lens, approximately 2,500 feet long, 500 feet in maximm
width, and having an area of approximately 15.6 acres, and to sampling of a roai
cut through the second largest lens, lying 300 feet east of: the main lens and

77 See Footnote 4, p. B51.

3087 -5-