History of Mining and Milling Practices 

and Production in San Juan County, 

Colorado, 1871–1991

By William R. Jones

Chapter C of

Integrated Investigations of Environmental Effects of Historical 

Mining in the Animas River Watershed, San Juan County, Colorado

Edited by Stanley E. Church, Paul von Guerard, and Susan E. Finger

Professional Paper 1651

U.S. Department of the Interior

U.S. Geological Survey
Contents

Abstract .........................................................................................................................................................43

Introduction...................................................................................................................................................43

Purpose and Scope .....................................................................................................................................54

Period I—The Smelting Era 1871–1889 ....................................................................................................54

Mining Development and Practices ................................................................................................54

Milling Development and Practices ................................................................................................55

Environmental Aspects ......................................................................................................................55

Period II—The Gravity Milling Era 1890–1913 .........................................................................................57

Mining Development and Practices ................................................................................................57

Milling Development and Practices ................................................................................................59

Environmental Aspects ......................................................................................................................61

Period III—The Early Flotation Era 1914–1935 ........................................................................................65

Mining Development and Practices ................................................................................................65

Milling Development and Practices ................................................................................................66

Environmental Aspects ......................................................................................................................67

Period IV—The Modern Flotation Era 1936–1991 ...................................................................................70

Mining Development and Practices ................................................................................................70

Milling Development and Practices ................................................................................................76

Environmental Aspects ......................................................................................................................77

Conclusions...................................................................................................................................................83

References Cited..........................................................................................................................................84

Appendix........................................................................................................................................................86

Notes on the Table and Chart of Reported and Estimated Mine Production ............................86

Author Information and Notes on Sources of Photographs ........................................................86

Figures

 1. Map showing mine localities, Animas River watershed study area ..................................50

 2. Map showing mills, smelters, tramways, and railroads .......................................................51

 3. Graphs showing historical production for San Juan County, 1871–1991 ..........................56

 4–20. Photographs showing:

 4. Sacking sorted crude ore for shipment to the smelter (circa 1904) ............................57

 5. Miners working inside a cut-and-fill stope, Gold King mine (circa 1899) ..................58

 6. Durango Smelter along the Animas River, 1906 .............................................................59

 7. Kendrick-Gelder (Ross) Smelter in Silverton and SG&N railroad (circa 1907) .........60

 8. Iowa aerial tram, Arrastra Creek (1925) ...........................................................................61

 9. Silverton Northern Railroad and the Sunnyside mine’s first “zinc train” (1915) .......62

 10. Silver Lake Mill # 2 and tram along the Animas River and Silverton and 

 Northern Railroad (circa 1904) ..........................................................................................62

 11. Two five-stamp crushers at Intersection Mill, head of Minnie Gulch (2003) .............63

 12. Stamps and mercury amalgamation plates, Old Hundred Mill (circa 1907) ..............64
 13. Silver Lake and adjacent mines, mill, and mill tailings (circa 1907) ............................65

 14. Gold King Mill at Gladstone and Silverton, Gladstone, and Northern 

 Railroad (circa 1903) ...........................................................................................................66

 15. Silver Lake Mill # 1 discharging tailings into Silver Lake (circa 1904) ........................67

 16. Silver Lake in 1978 showing that tailings had been removed ......................................68

 17. Shrink stope mining in Shenandoah-Dives mine (1937) ................................................69

 18. Minerals Separation flotation cells, Mayflower Mill (1930) .........................................70

 19. Sunnyside Eureka Flotation Mill at Eureka, Colo. (circa 1925) .....................................71

 20. Mayflower Mill and reclaimed mill tailings (2002) ..........................................................72

 21. Cross section of Shenandoah-Dives mine in 1950 ................................................................73

 22–30. Photographs showing:

 22. 1940s dump reclamation on Shenandoah-Dives vein, Dives Basin ............................74

 23. Lake Emma and Sunnyside mine (circa 1940) .................................................................75

 24. Mill tailings spigots at tailings pond # 1, Mayflower Mill (circa 1934) ........................77

 25. Mill tailings pond # 1 sand wall at Mayflower Mill (1936) .............................................78

 26. Failure of mill tailings pond # 1 dam at Mayflower Mill (1947) .....................................79

 27. Lake Emma after collapse into Sunnyside mine, June 11, 1978 ...................................80

 28. American tunnel portal, June 5, 1978, the day after Lake Emma flood .......................81

 29. Erosion trench and muddy discharge at American tunnel portal ...............................82

 30. Crossing muddy waters of Cement Creek, June 5, 1978, the day after 

 Lake Emma flood ..................................................................................................................83

Tables

 1. Summary of metal production from mines in San Juan County, Colorado,

from 1871 to 1991 .........................................................................................................................44

 2. Mills and smelters, San Juan County ......................................................................................52

 3. Aerial tramways built in San Juan County .............................................................................54

 4. Narrow gauge railroads built in San Juan County ................................................................55

Abstract

The history of mining and milling practices and production in San Juan County, Colorado, can be divided into four 

time periods based on the changes in milling technology. These 

periods are defined as (1) the Smelting Era 1871–1889, (2) the 

Gravity Milling Era 1890–1913, (3) the Early Flotation Era 

1914–1935, and (4) the Modern Flotation Era 1936–1991. During these periods mining production was influenced by national 

and world events such as war, metals prices, government policies, and mining and milling technology. During the Smelting 

Era, mines were small, milling was rarely done, and most ore 

was shipped as crude ore directly to the smelters. Selective mining left mineralized rock on surface dumps, and underground 

as stope backfill. Production in this period was an estimated 

93,527 short tons. During the Gravity Milling Era, higher 

capacity mining technologies were developed, and milling 

of low-grade ores became common. New technologies, including aerial tramways, air-powered drills, electrical devices, and 

an integrated narrow gauge railroad system helped increase productivity. Mine production in the period increased to 4.3 million 

short tons, of which more than 96 percent was waste; that 

96 percent was discharged directly into the Animas River and 

tributaries as mill tailings. During the Early Flotation Era, continued mining technology improvements allowed bulk mining 

of low-grade ore, which was milled rather than discarded on 

dumps. Tunnels and workings increased in extent. Production in 

this era totaled 4.2 million short tons. Mill tailings continued to 

be discharged into rivers and streams. In the Modern Flotation 

Era, milling efficiencies improved and production tonnages 

increased further, but owing to changes in the attitudes of the 

public and the courts, mill tailings were impounded in tailings ponds, rather than discharged to the Animas River. Long 

haulage tunnels became practical and drained ground water 

in the vicinity of the mine workings. Mining in the county 

increased as a result of World War II and Korean War government incentives, but it decreased after 1953, as costs increased 

and metals prices failed to keep pace. Increased environmental 

regulation of mining impacted the industry as reclamation costs 

reduced profitability. High gold prices and ore grades helped the 

Sunnyside mine remain in production until 1991 when mining 

ended in the county after 121 years. Production for the modern 

flotation era totaled 9.5 million short tons.

Total ore production for 1871–1991 is estimated at 

18.1 million short tons, of which an estimated 8.6 million short 

tons of mill tailings was discharged into the Animas River and 

tributaries.

Introduction

Silverton and San Juan County have a history of mining 

production that spans more than 120 years, from initial discoveries in 1871 to the end of major production in 1991. During 

this time the industry evolved and grew, owing to a complex 

mix of technology and economics influenced in the broadest 

sense by America’s need for metals. The mining industry has 

always been a leader in technological innovation and the industry around Silverton was no exception. Four distinct periods 

of mining and milling practices can be identified: 1871–1889; 

1890–1913; 1914–1935; and 1936–1991. Total production for 

the mines in San Juan County is listed in table 1.2

 These four 

periods are best defined by the ore processing and milling 

methods in use during the period. Mining techniques changed 

somewhat more gradually, but they maintained a clear connection to the demands placed on the mines by the rapid innovations of mineral processing technology. Mines in the study area 

are shown in figure 1, and the mills and smelters in figure 2. 

(See Church, Mast and others, this volume, Chapter E5.) Data 

on the type of mill, capacity, and processes used and dates of 

construction or expansion are in table 2. Tramways (table 3 and 

fig. 2) were constructed to provide efficient transport of the ore 

to larger and more efficient mills, and narrow gauge railroads 

(table 4 and fig. 2) facilitated in moving the ore concentrate to 

smelters outside the upper Animas River, Mineral Creek, and 

Cement Creek basins.

Chapter C

History of Mining and Milling Practices and Production 

in San Juan County, Colorado, 1871–1991

By William R. Jones1

2

Owing to space constraints, values for each commodity (troy oz × $/oz; 

lb × $/lb) are omitted here, and average values for silver, copper, and lead, 

originally computed to three decimal places, were rounded. The complete 

table appears on the database disk that accompanies the volume. 1

Silverton, Colo.
Year

No. of 

lode 

mines 

Crude 

ore 

treated

Total ore 

treated Gold Silver Copper Lead Zinc

Short

tons

Short 

tons

Troy

ounces

Average 

value

($/T Oz)

Troy

ounces

Average 

value

($/T Oz)

Lb

Average 

value

($/lb)

Lb

Average 

value

($/lb)

Lb

Average 

value

($/lb)

1871 -- -- 27 196 $20.67

1872 -- -- 100 701 $20.67

1873 -- -- 100 629 $20.67

1874 -- -- 100 461 $20.67 3,166 $1.28

1875 -- -- 1,100 483 $20.67 68,547 $1.24 120,000 $0.06

1876 -- -- 800 242 $20.67 48,465 $1.16 249,348 $0.06

1877 -- -- 800 242 $20.67 34,010 $1.20 8,664 $0.19 400,000 $0.06

1878 -- -- 600 290 $20.67 24,569 $1.15 36,145 $0.17 400,000 $0.04

1879 -- -- 900 290 $20.67 30,938 $1.12 100,000 $0.19 500,000 $0.04

1880 -- -- 700 290 $20.67 11,602 $1.15 100,000 $0.21 430,000 $0.05

1881 -- -- 600 242 $20.67 19,336 $1.13 100,000 $0.18 140,000 $0.05

1882 -- -- 1,100 483 $20.67 46,406 $1.14 100,000 $0.19 320,000 $0.05

1883 -- -- 7,400 1,693 $20.67 270,703 $1.11 100,000 $0.17 1,137,000 $0.04

1884 -- -- 8,000 1,935 $20.67 464,062 $1.11 300,000 $0.13 3,400,000 $0.04

1885 -- -- 14,000 1,935 $20.67 700,000 $1.07 100,000 $0.11 5,300,000 $0.04

1886 -- -- 14,700 6,908 $20.67 718,523 $0.99 100,000 $0.11 4,300,000 $0.05

1887 -- -- 9,000 5,865 $20.67 401,760 $0.98 300,000 $0.14 2,040,145 $0.05

1888 -- -- 7,500 9,208 $20.67 223,339 $0.94 240,000 $0.17 2,382,358 $0.04

1889 -- -- 26,000 19,103 $20.67 508,328 $0.94 135,018 $0.14 4,096,887 $0.04

1890 -- -- 67,000 9,064 $20.67 321,340 $1.05 147,354 $0.16 3,462,158 $0.05

1891 -- -- 121,000 9,294 $20.67 769,545 $0.99 235,467 $0.13 6,857,544 $0.04

1892 -- -- 73,000 7,204 $20.67 397,589 $0.87 136,768 $0.12 6,406,665 $0.04

1893 -- -- 89,000 12,611 $20.67 327,153 $0.78 1,125,826 $0.11 8,000,000 $0.04

1894 -- -- 76,000 16,450 $20.67 351,114 $0.63 1,118,222 $0.10 4,000,000 $0.03

1895 -- -- 230,000 41,094 $20.67 1,894,453 $0.65 2,057,588 $0.11 8,098,800 $0.03

1896 -- -- 241,000 43,962 $20.67 2,228,031 $0.68 845,094 $0.11 5,634,586 $0.03

1897 -- -- 163,000 33,591 $20.67 1,101,907 $0.60 1,435,203 $0.12 8,021,414 $0.04

1898 -- -- 232,000 54,794 $20.67 1,048,499 $0.59 2,252,421 $0.12 14,659,999 $0.04

1899 -- -- 237,000 48,199 $20.67 1,191,857 $0.60 1,197,661 $0.17 16,011,677 $0.05

1900 -- -- 205,000 36,633 $20.67 681,317 $0.62 1,972,087 $0.17 17,579,177 $0.04

1901 -- -- 242,850 46,588 $20.67 784,218 $0.60 2,740,042 $0.17 15,473,187 $0.04

1902 -- -- 230,000 73,741 $20.67 838,102 $0.53 3,012,283 $0.12 7,699,883 $0.04

1903 -- -- 249,500 82,758 $20.67 781,358 $0.54 2,939,018 $0.14 6,969,093 $0.04

1904 31 -- 233,663 83,997 $20.67 1,042,044 $0.58 3,467,124 $0.13 9,288,643 $0.04 1,384,340 $0.05

1905 20 -- 204,139 50,840 $20.67 750,844 $0.61 2,274,109 $0.16 8,045,126 $0.05 248,627 $0.06

1906 26 -- 196,438 43,545 $20.67 690,076 $0.68 1,549,663 $0.19 4,515,317 $0.06 584,476 $0.06

1907 27 -- 235,639 46,814 $20.67 1,175,176 $0.66 2,450,280 $0.20 12,483,507 $0.05 237,677 $0.06

1908 42 4,411 202,643 48,269 $20.67 1,004,287 $0.53 2,282,738 $0.13 8,402,569 $0.04 10,131 $0.05

1909 40 6,100 187,041 33,053 $20.67 793,637 $0.52 1,653,192 $0.13 9,085,068 $0.04 786,518 $0.05

1910 53 6,052 206,272 34,371 $20.67 782,250 $0.54 1,208,496 $0.13 10,688,386 $0.04 3,781,259 $0.05

1911 37 1,919 108,088 16,276 $20.67 325,604 $0.53 470,912 $0.13 6,933,822 $0.05 2,224,351 $0.06

1912 41 -- 140,917 25,327 $20.67 714,974 $0.62 1,063,291 $0.17 9,114,334 $0.05 2,478,594 $0.07

1913 38 10,832 123,343 31,811 $20.67 880,409 $0.60 1,221,516 $0.16 9,508,979 $0.04 1,664,999 $0.06

1914 29 4,675 117,988 24,597 $20.67 493,917 $0.55 825,180 $0.13 5,199,000 $0.04 971,177 $0.05

1915 42 5,952 147,878 28,235 $20.67 430,637 $0.51 1,054,463 $0.18 6,791,596 $0.05 2,259,226 $0.12

1916 46 11,748 146,128 21,218 $20.67 502,342 $0.66 1,615,167 $0.25 7,285,304 $0.07 4,014,403 $0.13

1917 46 -- 145,685 15,383 $20.67 658,261 $0.82 1,665,923 $0.27 10,515,535 $0.09 3,270,500 $0.10

Table 1. Summary of metal production from mines in San Juan County, Colorado from 1871 to 1991.

[Data from 1871 to 1908 are estimated when italicized, see notes for details; total value of metals italicized where calculated from commodity prices; --, no data; 

$/T Oz, dollars per troy ounce; $/lb, dollars per pound]

44 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 45

Total value 

of metals 

produced

Sources 

of data

Important 

historical events

$4,050.00 Ransome (1901) Discovery of Little Giant mine.

$14,500.00 Ransome (1901)

$13,000.00 Henderson (1926)

$13,586.00 Henderson (1926)

$101,958.00 Henderson (1926) Greene Smelter opens in Silverton.

$76,429.00 Henderson (1926)

$69,458.00 Henderson (1926)

$54,654.00 Henderson (1926) Bland-Allison Silver Purchase Act.

$79,751.00 Henderson (1926) Smelter moved to Durango.

$62,242.00 Henderson (1926)

$51,770.00 Henderson (1926) 

$97,683.00 Henderson (1926) D&RG Railroad arrives in Silverton.

$400,871.00 Henderson (1926)

$719,909.00 Henderson (1926)

$1,006,500.00 Henderson (1926)

$1,063,037.00 Henderson (1926)

$648,176.00 Henderson (1926)

$545,411.00 Henderson (1926) Silverton RR built to Red Mountain district.

$1,050,707.00 Henderson (1926)

$703,548.00 Henderson (1926) Sherman Silver Purchase Act passed.

$1,278,973.00 Henderson (1926)

$766,943.00 Henderson (1926)

$933,436.00 Henderson (1926) Repeal of Sherman Silver Purchase Act.

$799,456.00 Henderson (1926)

$2,560,129.00 Henderson (1926) Silverton Northern RR built to Eureka for Sunnyside mine.

$2,684,076.00 Henderson (1926)

$1,816,465.00 Henderson (1926)

$2,587,586.00 Henderson (1926)

$2,636,712.00 Henderson (1926) SG&N RR built to Gladstone for Gold King mine.

$1,280,471.00 Henderson (1926)

$2,556,439.00 Henderson (1926) 

$2,651,614.00 Henderson (1926)

$2,827,888.00 Henderson (1926)

$2,860,421.00 Henderson (1926)

$2,251,535.00 Henderson (1926)

$1,969,695.00 Henderson (1926)

$2,999,623.00 Henderson (1926) Financial Panic of 1907.

$2,184,801.00 Henderson (1926)

$1,744,003.00 Henderson (1926)

$1,960,898.00 Henderson (1926)

$1,006,707.00 Henderson (1926)

$1,719,894.00 Henderson (1926)

$1,890,349.00 Henderson (1926)

$1,143,653.00 Henderson (1926) WWI begins in Europe.

$1,585,894.00 Henderson (1926)

$2,207,116.00 Henderson (1926)

$2,553,137.00 Henderson (1926) America enters WWI.
Year

No. of 

lode 

mines 

Crude 

ore 

treated

Total ore 

treated Gold Silver Copper Lead Zinc

Short

tons

Short 

tons

Troy

ounces

Average 

value

($/T Oz)

Troy

ounces

Average 

value

($/T Oz)

Lb

Average 

value

($/lb)

Lb

Average 

value

($/lb)

Lb

Average 

value

($/lb)

1918 37 -- 132,927 12,432 $20.67 477,322 $1.00 1,120,178 $0.25 9,485,775 $0.07 3,410,308 $0.09

1919 20 2,849 64,899 6,412 $20.67 279,667 $1.12 661,667 $0.19 5,443,906 $0.05 1,833,768 $0.07

1920 19 2,016 201,671 12,904 $20.67 746,100 $1.09 1,361,391 $0.18 16,601,025 $0.08 11,837,395 $0.08

1921 17 1,164 1,164 400 $20.67 64,179 $1.00 28,558 $0.13 557,555 $0.05 - $0.05

1922 26 2,758 8,808 1,246 $20.67 77,864 $1.00 110,348 $0.14 1,651,982 $0.06 1,300,000 $0.06

1923 16 627 153,114 11,706 $20.67 471,750 $0.82 1,005,441 $0.15 10,738,943 $0.07 9,540,000 $0.07

1924 13 497 233,790 19,557 $20.67 689,656 $0.67 1,601,748 $0.13 1,755,913 $0.08 17,579,000 $0.07

1925 17 748 274,783 15,089 $20.67 808,254 $0.69 1,502,000 $0.14 2,083,400 $0.09 22,200,000 $0.08

1926 15 372 289,401 14,309 $20.67 869,963 $0.62 1,560,400 $0.14 18,460,600 $0.08 22,423,000 $0.08

1927 10 290 282,824 12,235 $20.67 726,291 $0.57 1,549,214 $0.13 17,271,016 $0.06 22,869,000 $0.06

1928 9 255 326,110 15,739 $20.67 827,318 $0.59 1,755,653 $0.14 16,694,449 $0.06 25,427,000 $0.06

1929 13 130 346,866 20,869 $20.67 871,544 $0.53 2,157,000 $0.18 19,012,224 $0.06 22,858,000 $0.07

1930 12 245 403,801 31,994 $20.67 1,067,496 $0.39 2,678,000 $0.12 17,788,600 $0.05 19,677,000 $0.05

1931 10 26 172,430 31,308 $20.67 430,793 $0.29 1,250,505 $0.08 1,134,000 $0.04 - $0.04

1932 9 -- 191,051 24,724 $20.67 339,965 $0.28 1,367,000 $0.06 1,031,000 $0.03 - $0.03

1933 12 61 199,612 23,474 $25.56 389,642 $0.35 1,184,000 $0.06 1,198,400 $0.04 - $0.04

1934 16 781 210,489 16,592 $34.95 303,012 $0.65 819,300 $0.08 2,051,000 $0.04 2,000 $0.04

1935 15 1,038 177,373 16,128 $35.00 282,418 $0.72 624,000 $0.08 2,418,200 $0.04 - $0.04

1936 25 868 204,281 22,162 $35.00 432,603 $0.78 991,400 $0.09 3,112,900 $0.05 - $0.05

1937 20 473 283,859 25,099 $35.00 484,362 $0.77 1,102,000 $0.12 6,680,000 $0.06 3,856,000 $0.07

1938 21 482 331,725 26,516 $35.00 647,712 $0.65 2,021,000 $0.10 8,011,000 $0.05 8,549,000 $0.05

1939 20 510 199,271 16,152 $35.00 286,150 $0.68 1,013,000 $0.10 2,092,000 $0.05 1,166,000 $0.05

1940 33 -- 231,630 16,098 $35.00 362,662 $0.71 739,000 $0.11 5,378,000 $0.05 2,971,000 $0.06

1941 25 216 265,232 17,384 $35.00 532,731 $0.71 870,000 $0.12 6,145,000 $0.06 1,680,000 $0.08

1942 16 341 197,404 17,094 $35.00 394,657 $0.71 575,000 $0.12 4,297,000 $0.07 784,000 $0.09

1943 19 180 202,100 21,214 $35.00 327,098 $0.71 498,000 $0.13 5,397,000 $0.08 1,004,000 $0.11

1944 11 85 176,695 28,523 $35.00 233,027 $0.71 348,000 $0.14 4,594,000 $0.08 1,258,000 $0.11

1945 12 94 196,106 21,923 $35.00 306,374 $0.71 466,000 $0.14 5,371,000 $0.09 1,690,000 $0.12

1946 15 127 242,841 17,396 $35.00 361,328 $0.81 757,000 $0.16 7,084,000 $0.11 3,757,000 $0.12

1947 20 184 236,817 20,123 $35.00 417,451 $0.91 789,900 $0.21 5,797,100 $0.14 3,607,600 $0.12

1948 30 2,969 228,386 16,471 $35.00 542,490 $0.91 654,000 $0.22 6,004,000 $0.18 3,332,000 $0.13

1949 31 403 244,368 11,549 $35.00 584,068 $0.91 608,000 $0.20 7,026,000 $0.16 3,198,000 $0.12

1950 25 426 278,152 13,902 $35.00 596,149 $0.91 690,000 $0.21 6,784,000 $0.14 2,590,000 $0.14

1951 28 322 243,917 9,998 $35.00 453,327 $0.91 1,102,000 $0.24 9,064,000 $0.17 3,684,000 $0.18

1952 20 55 190,599 10,203 $35.00 363,530 $0.91 1,190,000 $0.24 8,446,000 $0.16 2,942,000 $0.17

1953 12 -- 55,943 2,696 $35.00 122,462 $0.91 272,000 $0.29 2,958,000 $0.13 1,264,000 $0.12

1954 7 217 6,900 491 $35.00 20,395 $0.91 24,000 $0.30 458,000 $0.14 166,000 $0.11

1955 8 14 10,408 455 $35.00 35,829 $0.91 78,000 $0.37 938,000 $0.15 492,000 $0.12

1956 8 17 19,780 841 $35.00 37,283 $0.91 85,600 $0.43 1,665,800 $0.16 1,287,400 $0.14

1957 8 165 17,245 2,180 $35.00 54,757 $0.91 131,700 $0.30 1,124,800 $0.14 624,100 $0.12

1958 7 -- 17,049 1,205 $35.00 33,336 $0.91 96,000 $0.26 782,000 $0.12 548,000 $0.10

1959 3 -- 6,049 310 $35.00 7,303 $0.91 46,000 $0.30 290,000 $0.12 220,000 $0.12

1960 5 -- 39,861 1,206 $35.00 50,284 $0.91 322,000 $0.32 778,000 $0.12 84,000 $0.13

1961 12 -- 2,531 221 $35.00 5,740 $0.93 32,000 $0.30 80,000 $0.11 44,000 $0.12

1962 4 -- 42,716 411 $35.00 31,306 $1.08 78,000 $0.31 1,578,000 $0.10 2,104,000 $0.12

1963 4 -- 134,971 1,249 $35.00 127,497 $1.28 528,000 $0.31 5,878,000 $0.11 8,188,000 $0.12

1964 7 -- 174,333 1,239 $35.00 194,724 $1.29 1,064,000 $0.32 8,214,000 $0.14 13,452,000 $0.14

Table 1. Summary of metal production from mines in San Juan County, Colorado from 1871 to 1991.—Continued

46 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 47

Total value 

of metals 

produced

Sources 

of data

Important 

historical events

$1,994,845.00 Henderson (1926) Sunnyside Flotation Mill at Eureka begins production.

$991,249.00 Henderson (1926)

 $3,617,422.00 Henderson (1926)

 $101,225.00 Henderson (1926) Post war recession closes most mines.

 $283,479.00 Henderson (1926)

 $2,117,067.00 Henderson (1926) Sunnyside mine reopens.

 $3,623,610.00 USBM Min.Res. of the U.S. 1924, commodity prices from Ingram (1932)

 $4,585,890.00 USBM Min.Res. of the U.S. 1925, commodity prices from Ingram (1932)

 $4,215,674.00 USBM Min.Res of the U.S. 1926, commodity prices from Ingram (1932)

 $3,419,371.00 USBM Min.Res.of the U.S. 1927, commodity prices from Ingram (1932) Shenandoah-Dives mine opens.

 $3,583,035.00 USBM Min.Res of the U.S. 1928, commodity prices from Ingram (1932)

 $3,981,967.00 USBM Min.Res of the U.S. 1929, commodity prices from Ingram (1932) Stock Market Crash; Mayflower Mill built.

 $3,254,428.00 USBM Min.Res of the U.S. 1930, commodity prices from Ingram (1932) Sunnyside mine closes, S-D mine and Mayflower Mill start 

production.

 $927,892.00 USBM Min.Res of the U.S. 1931, commodity prices from Ingram (1932) Great Depression begins.

 $724,013.00 USBM Minerals Yearbook 1932-33

 $741,740.00 USBM Minerals Yearbook 1934

 $917,294.00 USBM Minerals Yearbook 1935 Gold price increased to $35.00 per ounce.

 $915,988.00 USBM Minerals Yearbook 1936 

 $1,345,123.00 USBM Minerals Yearbook 1937 Tailings pond operations sucessful.

 $2,031,242.00 USBM Minerals Yearbook 1938 Sunnyside mine reopens. 

 $2,323,685.00 USBM Minerals Yearbook 1939 Sunnyside mine closes.

 $1,023,863.00 USBM Minerals Yearbook 1940 Strike closes Shenandoah-Dives mine.

 $1,360,903.00 Vanderwilt (1947)

 $1,566,196.00 USBM Minerals Yearbook 1941

 $1,309,321.00 USBM Minerals Yearbook 1942 America enters WWII; premiums paid on metal production.

 $1,553,145.00 USBM Minerals Yearbook 1943

 $1,721,925.00 USBM Minerals Yearbook 1944

 $1,704,337.00 USBM Minerals Yearbook 1945

 $2,253,957.00 USBM Minerals Yearbook 1946

 $2,519,279.00 USBM Minerals Yearbook 1947 Premium price plan expires.

 $2,727,256.00 USBM Minerals Yearbook 1948

 $2,559,262.00 USBM Minerals Yearbook 1949

 $2,453,255.00 USBM Minerals Yearbook 1950 Korean War begins.

 $3,265,458.00 USBM Minerals Yearbook 1951

 $2,822,276.00 USBM Minerals Yearbook 1952

 $816,116.00 USBM Minerals Yearbook 1953 Shenandoah-Dives mine closes, Korean War armistice.

 $123,398.00 USBM Minerals Yearbook 1954

 $277,724.00 USBM Minerals Yearbook 1955

 $537,463.00 USBM Minerals Yearbook 1956

 $398,742.00 USBM Minerals Yearbook 1957

 $244,953.00 USBM Minerals Yearbook 1958 

 $90,335.00 USBM Minerals Yearbook 1959, USGS (1999) Standard Uranium Corp. begins American tunnel.

 $292,847.00 USBM Minerals Yearbook 1960, USGS (1999) 

 $35,681.00 USBM Minerals Yearbook 1961, USGS (1999) American tunnel completed at Sunnyside mine.

 $459,266.00 USBM Minerals Yearbook 1962, USGS (1999) Production begins from Sunnyside mine through American 

tunnel.

 $1,945,755.00 USBM Minerals Yearbook 1963, USGS (1999)

 $3,547,585.00 USBM Minerals Yearbook 1964, USGS (1999)
Year

No. of 

lode 

mines 

Crude 

ore 

treated

Total ore 

treated Gold Silver Copper Lead Zinc

Short

tons

Short 

tons

Troy

ounces

Average 

value

($/T Oz)

Troy

ounces

Average 

value

($/T Oz)

Lb

Average 

value

($/lb)

Lb

Average 

value

($/lb)

Lb

Average 

value

($/lb)

1965 9 -- 182,704 2,052 $35.00 218,665 $1.29 906,000 $0.35 8,656,000 $0.16 17,316,000 $0.15

1966 13 -- 197,989 3,364 $35.00 252,979 $1.29 710,000 $0.36 9,492,000 $0.15 16,678,000 $0.14

1967 8 -- 211,979 1,742 $35.00 261,873 $1.55 738,000 $0.38 11,054,000 $0.14 17,084,000 $0.14

1968 9 -- 194,888 3,026 $40.06 247,123 $2.14 778,000 $0.41 7,948,000 $0.13 14,998,000 $0.14

1969 5 -- 214,735 6,090 $41.51 266,579 $1.79 888,000 $0.47 10,572,000 $0.15 15,416,000 $0.15

1970 7 -- 242,695 14,884 $36.41 271,758 $1.77 1,386,000 $0.58 13,138,000 $0.16 17,454,000 $0.15

1971 5 -- 191,154 14,703 $41.25 219,790 $1.55 1,096,000 $0.52 9,574,000 $0.14 10,402,000 $0.16

1972 1 -- 180,112 31,424 $58.60 291,204 $1.68 898,958 $0.51 10,040,542 $0.15 15,532,814 $0.18

1973 2 -- 191,350 30,926 $97.81 290,316 $2.56 686,000 $0.60 9,474,000 $0.16 12,872,000 $0.21

1974 2 -- 192,041 28,493 $159.74 237,476 $4.71 642,000 $0.77 7,062,000 $0.22 11,616,000 $0.36

1975 2 -- 186,615 27,689 $161.49 206,287 $4.42 584,000 $0.64 6,734,000 $0.21 9,324,000 $0.39

1976 1 -- 214,134 23,555 $125.32 235,547 $4.35 728,050 $0.70 7,280,555 $0.23 11,991,500 $0.37

1977 7 -- 268,957 49,410 $148.31 329,968 $4.62 1,004,000 $0.67 9,648,000 $0.31 9,878,000 $0.34

1978 1 -- 122,702 18,405 $193.55 196,323 $5.40 711,670 $0.66 4,908,080 $0.34 8,098,330 $0.31

1979 3 -- 20,082 2,410 $307.50 26,106 $11.09 80,330 $0.92 602,460 $0.53 923,770 $0.37

1980 3 -- 126,541 31,635 $612.56 202,466 $20.63 759,240 $1.01 4,302,390 $0.43 6,327,050 $0.37

1981 3 -- 198,616 35,070 $459.64 216,099 $10.52 846,820 $0.84 5,554,100 $0.37 6,407,680 $0.45

1982 3 -- 224,067 37,953 $375.91 284,391 $7.95 973,400 $0.73 9,151,220 $0.26 12,169,180 $0.39

1983 1 -- 274,579 39,739 $424.00 348,095 $11.44 1,155,740 $0.77 8,946,920 $0.22 12,054,980 $0.41

1984 1 -- 237,969 27,337 $360.66 360,510 $8.14 1,432,000 $0.67 9,632,000 $0.26 11,706,000 $0.49

1985 1 -- 19,360 4,840 $317.66 44,528 $6.14 174,240 $0.67 1,200,320 $0.19 1,626,240 $0.40

1986 1 -- 133,016 22,112 $368.24 211,183 $5.47 822,000 $0.66 4,730,000 $0.22 9,663,060 $0.38

1987 1 -- 255,712 47,093 $477.95 446,330 $7.01 2,251,620 $0.83 13,816,760 $0.36 18,422,350 $0.42

1988 1 -- 197,504 31,291 $438.31 395,033 $6.53 1,909,540 $1.21 10,695,320 $0.37 14,483,720 $0.60

1989 1 -- 179,391 29,612 $382.58 367,723 $5.50 1,817,800 $1.31 10,226,820 $0.39 16,037,060 $0.82

1990 1 -- 237,829 21,784 $384.93 346,378 $4.82 1,787,720 $1.23 10,632,700 $0.46 15,509,220 $0.75

1991 1 -- 141,534 19,940 $363.29 227,613 $4.04 1,267,500 $1.09 7,220,560 $0.34 10,807,640 $0.53

TOTAL 73,694 18,136,276 2,288,923 51,306,907 112,279,546 765,645,442 604,213,443

Table 1. Summary of metal production from mines in San Juan County, Colorado from 1871 to 1991.—Continued

48 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 49

Total value 

of metals 

produced

Sources 

of data

Important 

historical events

 $4,553,906.00 USBM Minerals Yearbook 1965, USGS (1999)

 $4,554,795.00 USBM Minerals Yearbook 1966, USGS (1999)

 $4,661,184.00 USBM Minerals Yearbook 1967, USGS (1999)

 $4,048,972.00 USBM Minerals Yearbook 1968, USGS (1999) Standard Metals announces plan to close Sunnyside mine.

 $4,978,000.00 USBM Minerals Yearbook 1969, USGS (1999) Gold discovered in Sunnyside mine.

 $6,548,203.00 USBM Minerals Yearbook 1970, USGS (1999)

 $4,512,584.00 USBM Minerals Yearbook 1971, USGS (1999) Standard Metals bankruptcy closes Sunnyside mine.

 $5,645,698.00 Standard Metals Corp 1973 Annual Report, production and total value; 

commodity prices from USGS (1999)

Standard reopens Sunnyside mine.

 $8,378,947.00 USBM Minerals Yearbook 1973, silver and base metal values calculated 

from commodity prices (USGS, 1999)

Government removes restrictions on gold price.

 $11,924,712.00 USBM Minerals Yearbook 1974, silver and base metal values calculated 

from commodity prices (USGS, 1999)

 $10,842,267.00 USBM Minerals Yearbook 1975, silver and base metal values calculated 

from commodity prices (USGS, 1999)

 $10,601,928.06 Sunnyside mine production only (Hutchinson, 1988); values calculated 

from commodity prices USGS (1999) 

Mayflower Mill increases capacity to 1000 short tons per day

 $15,883,716.00 USBM Minerals Yearbook 1977, silver and base metal values calculated 

from commodity prices (USGS, 1999) 

 $7,136,916.00 Sunnyside mine production from Hutchinson (1988); total value from 

Standard Metals 1982 report

Lake Emma floods Sunnyside mine.

 $2,129,133.00 Sunnyside mine production from Hutchinson (1988); total value from 

Standard Metals 1982 report

 $17,904,380.00 Sunnyside mine production from Hutchinson (1988); total value from 

Standard Metals 1982 report

Sunnyside mine reopens.

 $24,882,000.00 Production from Standard Metals 1984 Report, Sunnyside mine only. 

Total value from USBM Yearbook 1983

 $25,895,000.00 Producton from Standard Metals 1984 Report, Sunnyside mine only. 

Total value from USBM Yearbook 1984

 $21,019,112.00 Production from Standard Metals 1984 Annual Report; value from 1986 

backruptcy disclosure 

 $21,905,397.82 Production from Standard Metals 1984 Annual Report; values calculated 

from commodity prices (USGS, 1999)

 $2,813,704.96 Sunnyside mine production from Hutchinson (1988); values calculated 

from commodity prices (USGS, 1999)

Standard Metals bankruptcy closes Sunnyside mine.

 $14,718,148.80 USBM Minerals Yearbook 1986 except zinc from Hutchinson (1988); 

commodity prices from USGS (1999)

Echo Bay Mines purchases, reopens Sunnyside mine.

 $40,173,640.64 Base metal production from Hutchinson (1988), tonnage, gold, and silver 

from Echo Bay Mines 1987 Annual Report

 $31,282,882.56 Sunnyside Gold Corp. (written commun., 2002); commodity prices and 

value calculated from USGS (1999)

 $32,910,691.94 Sunnyside Gold Corp. (written commun., 2002); commodity prices and 

value calculated from USGS (1999)

 $28,716,460.52 Sunnyside Gold Corp. (written commun., 2002); commodity prices and 

value calculated from USGS (1999)

 $17,674,258.14 Sunnyside Gold Corp. (written commun., 2002); commodity prices and 

value calculated from USGS (1999)

Sunnyside mine closes August 15, 1991.

 $529,838,329.44 
Howardsville

Gladstone

Chattanooga Eureka

Animas

Forks

Silverton

107o48' 107o32'

37o

52'

30"

37o

45'

107o40'

Animas River

watershed 

study area

C O L O R A D O

Durango

0

0

1

2

3

4

5 MILES

6 8 KILOMETERS

Animas River

An

mi as

River

South

Fork Mineral Creek

Mineral Creek

Cement Creek

181

116

120

19

111

96 106

Lake

Emma

294

228

343

345 348

303

350

355

359

319

239

325

Mine

Watershed study area

 boundary

EXPLANATION

359

Arr astra Creek

Cunningham

Creek

Figure 1. Locality map of mines, Animas River watershed study area (Church, Mast, and others, this volume, Chapter E5). Mine 

sites referred to in this chapter are: Frisco tunnel (site # 19), Gold King Mill level tunnel (site # 96), Lead Carbonate (mine # 106), Gold 

King (mine # 111), Sunnyside (mine # 116), Terry tunnel, Sunnyside (mine # 120), May Day (mine # 181), Little Nation (mine # 228), Old 

Hundred mine, mill level (site # 239), Unity tunnel of the Silver Lake (mine # 294), Little Giant (mine # 303), Pride of the West mine, 

# 1 level (mine # 319), Buffalo Boy (mine # 325), Silver Lake mine, # 1 level (mine # 343), Iowa (mine # 345), Royal Tiger (mine # 348), 

North Star (mine # 350, later a part of the Shenandoah-Dives mine, 1700 level), Shenandoah-Dives mine, 900 level (mine # 355), and 

Highland Mary mine, # 7 level (mine # 359).

50 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 51

97

93 94

95

151

185

184

286

287

224

299

297 307

310 309

347

282

277

264

267 275

502 361

316 318

240 242

237 238

510 509

215

508 507

219

222

221

225

227

231 233

234

191

192

194

166

165 164 158

113

51

52 55 63

20 24 26

27

28

66

124

213

214

138

205 328

512

EXPLANATION

107o48' 107o32'

37o

52'

30"

37o

45'

107o40'

Mill tailings

Smelter

Mill

Mine

Howardsville

Gladstone

Eureka

Chattanooga

Animas

Forks

Animas River

watershed 

study area

C O L O R A D O

Durango

Railroad

E Tramway

Watershed study area

 boundary

0

0

1

2

3

4

5 MILES

6 8 KILOMETERS

Silverton M ni eral Creek

C

me ent Creek

Animas Riv er

C

A

FF HH

GG

Z

W

X

Y

T

U

V

N

P O

Q

R

S

F

D

E

I

J

K

L

M

AA

DD

EE

B

G

H

CC

BB

II

E

Lake

Emma

Figure 2. Locality map of mills, smelters, tramways, and railroads (mill and smelter localities from Church, Mast, and others, this 

volume; railroads from Sloan and Skowronski, 1975). Mills, their processing capacities, and dates of construction or expansion 

are summarized in table 2. Trams and their dates of construction are in table 3. Narrow gauge railroad segments and dates of 

their construction are in table 4. Large mill tailings present today are the Kittimack tailings (site # 192), Pride of the West Mill [# 4] 

tailings (permitted; site # 234), Old Hundred tailings (site # 237), Lackawanna tailings (site # 286, removed by the U.S. Bureau of Land 

Management in 2000 to the May Day mine site # 181, fig. 1), North Star tailings (site # 310), and Highland Mary tailings (site # 361).
Name Site No. 

(fig. 2)

Mill method 

(Stamp, 

Concentrator, 

or Flotation)

Date built 

or enlarged

 Capacity 

(tons/day)

Amalgamation 

(used mercury 

for gold 

recovery)

Bagley Mill (aka Frisco) 20 C 1912 150 N

Big Giant Mill 307 C c. 1896 20–40 Y

Boston & Silverton Mill (aka Yukon) 185 S, C 1890s 75 ?

Columbus Mill 24 F 1940s 50 N

Contention Mill (aka Arpad, North Star [#2] ) 225 S,C c. 1905 100 N

Green Mountain Mill (Osceola) 240 C 1904 300 N

Gold King Mill 94 S, C c. 1897, 1899,

1903, 1904

65, 100, 

250, 325

Y

Gold Prince Mill 27 S,C 1905–1906 500 Y

Hamlet Mill 191 C c. 1905 50, 75 N

Hanson Mill (aka Sunnyside Extension Mill) 51 S, C 1896 50 N

Hercules Mill (aka Empire) 277 S, C 1889, 1899 50, 100, 

140, 200

Y

Highland Mary Mill (aka Gold Tunnel M & M) 502 C, F 1902, 1940, 

1944

150, 100 N

Ice Lake Mill 205 S, C 1890s 40 Y

Intersection Mill 328 S, C 1890s 30 Y

Iowa Mill 297 C 1890s, 1901 50, 100, 

150, 200

Y

Kittimack Mill 194 C c. 1908 100 N

Lackawanna Mill 287 C, F 1920s 50 N

Lead Carbonate Mill 95 F 1947 50 N

Little Giant Mill 299 Rolls/pan 1873 5 Y

Little Nation Mill 231 C, F 1923 50 N

Mastodon Mill 52 F 1952 50 ?

Mayflower Mill (aka Shenandoah-Dives Mill) 221 F, C 1929, 1935, 

1944, 1976

300, 600, 

750, 1,200

Y

Mears-Wilfley Mill 222 C, F 1914 500 N

Mogul Mill 93 C 1900 75 N

Natalie/Occidental Mill 151 S, C 1899 75 N

North Star (Sultan) Mill 264 S, C 1883 70, 100 Y

North Star (Soloman) Mill [#1] 309 S 1882 40 ?

Old Hundred Mill 238 S, C, F 1905, 1950 200, 65 Y

Pride of the West Mill [#1] (Schoelkopf) 318 S 1881 20 ?

Pride of the West Mill [#2] (aka Howardsville Conc.) 227 S, F 1901 40 ?

Pride of the West Mill [#3] 316 F 1928 65 N

Pride of the West Mill [#4] (aka Dixilyn, P&G) 233 F 1940, 1968, 

1981

50, 90, 

300

N

Red and Bonita Mill 97 S 1899 75 ?

Silver Lake Mill #1 347 S, C 1893, 1899, 

1901

100, 200, 

250

N

Silver Lake Mill #2 219 C, F 1900, 1902, 

1907, 1914

200, 300, 

450

N

Silver Ledge Mill 138 C 1883, 1898, 

1902

50, 125, 

200

N

Table 2. Mills and smelters, San Juan County.

[Localities shown in fig. 2; dates mill built or enlarged where approximate are indicated; size of mill capacity in italics where estimated; mercury used in gold 

recovery indicated by Y (yes) or N (no) if known, ? if uncertain; method of ore processing, C, concentrator; F, Flotation, S, Stamps; Lix, Lixivation; Rolls/pan, 

rolls crusher and pan amalgamation]

52 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 53

Mining in Silverton followed the “boom and bust” pattern associated with the mining industry. International and 

national events such as war, economic depression, and government policies often triggered these cycles, which were quickly 

reflected in the price of metals and subsequent production. 

Ores in the district are typically polymetallic, containing 

gold, silver, lead, copper, zinc, cadmium, iron, and other trace 

metals. Mining evolved from small “high-grade” mines with 

limited processing, to larger mines producing lower grade 

ores, but at lower cost. This increasing output was processed 

in mills, which grew in size and efficiency. But unlike many 

other mining areas, which continued this progressive increase 

in size, large mines in San Juan County reached an upper limit 

of 700–1,000 short tons of ore produced per day around 1920. 

Annual production in the county was remarkably steady at 

200,000–250,000 short tons per year when economic conditions were favorable to sustain profitable mining operations in 

the county (table 1 and fig. 3).

The sources of this production were varied, but a 

pattern developed that remained typical to the end of mine 

production in 1991: one or two “large” mines would account 

for the majority of production in any single year. Note that 

production records for individual mines are not generally 

available. After 1930, only two mines, the Shenandoah-Dives 

(1930–1953; mine # 355), which produced 4.099 million 

short tons of ore (Varnes, 1963) and Sunnyside (1962–1991, 

mine # 116 and # 96), which produced more than 7 million 

short tons of ore (Sunnyside Gold Corp., written commun., 

2002) account for around 90 percent of all mine production for these years. Other earlier “large” mines include 

the Pride of the West (mine # 319—346,000 tons; Varnes, 

1963), Silver Lake (mine # 343 and # 294—849,000 tons; 

Varnes, 1963), Iowa and Royal Tiger mines (mine # 345 

and # 348—376,000 tons; Varnes, 1963), and the Gold 

King (mine # 111—665,000 tons; Taylor, 1988). Numerous small mines added to production during periods of high 

Name Site No. 

(fig. 2)

Mill method 

(Stamp, 

Concentrator, 

or Flotation)

Date built 

or enlarged

 Capacity 

(tons/day)

Amalgamation 

(used mercury 

for gold 

recovery)

Silver Wing Mill 124 S, C 1898 40, 100 N

Sound Democrat Mill 55 S, C c. 1900 30 Y

Sunnyside Eureka Mill 164 F 1917, 1925 600, 750, 

1,100

N

Sunnyside Mill #1 (Midway) 158 S, C 1889 40, 50 Y

Sunnyside Mill #2 165 S, C, F 1899, 1901, 

1915

40, 50, 

150, 200

Y

Sunnyside-Thompson Mill 113 S, C 1888 20 Y

Titusville Mill* C c. 1896 85 ?

Treasure Mountain Mill 63 F 1941 25 N

Vertex Mill 242 F 1929 100 N

Victoria Mill 267 S, C 1890s 100 Y

Ward and Shepard Mill 224 S 1881 10–20 Y

William Crooke Mill 215 S, Lix, C c. 1882 50 N

Yukon Mill 184 F, C 1977 10 N

San Juan Smelting Co. 26 1874

Brown, Epley & Co. Smelter 28 1876

Eclipse Smelter 66 1880

Greene & Co. Smelter 214 1874

Kendrick-Gelder Smelter (Ross) 213 1900

Martha Rose Smelter 275 1882, 1894

Rough & Ready Smelter 282 1875

Winspear Smelter 166 1878 

*

Locality uncertain, assumed to be at terminus of Titusville tram (FF, table 3, fig. 2).

Table 2. Mills and smelters, San Juan County.—Continued
Period I—The Smelting Era 1871–1889

Mining Development and Practices

Lode mining began in 1871 with the discovery of the 

Little Giant (mine # 303, fig. 2 and table 2) in Arrastra Creek. 

Mining was performed by hand methods in small operations 

producing only a few tons of ore per day. Shafts, adits, and 

cuts were excavated directly into exposed or near-surface 

outcrops. Tunnels and shafts were short, typically not more 

than a few hundred feet. Only the higher grade ore was mined, 

usually the silver-lead ores. Lower grade ores and waste were 

typically left unmined when possible. Little mechanical processing or milling was done at the mine. The best ores were 

sacked and hauled off the mountains with mules as “crude 

ore” and eventually shipped to smelters as far away as Wales 

in the United Kingdom (fig. 4).

Ores were typically hand sorted, meaning the best 

ore chunks were hand selected and separately shipped to 

the smelters as “first class ore.” The sorting was done both 

underground in the stopes and at the surface in sorting houses 

(fig. 4). Often, a slightly lower grade ore was again hand 

sorted and shipped as “second class ore.” The hand “cobbing” 

technique upgraded lower grade ores when miners hammered 

off chunks of good ore mineral from the lower grade ore and 

waste rock. After the cobbed-off chunks were sacked, the 

mine waste was deposited on the surface dumps. To provide 

a work surface in the stopes, the void left from ore extraction 

was filled with mine waste and low-grade ores in a mining 

method called “cut-and-fill stoping” (Ransome, 1901). Owing 

to the difficulty and cost of breaking rock, mine development 

avoided tunneling through unmineralized, valueless “country” 

rock. Thus, much waste rock left both underground in stopes 

and on surface mine-waste dumps contained a significant 

amount of mineralized rock (fig. 5).

As the period progressed, mines became larger as outside 

capital financed new mines and expansion of existing mines. 

The Greene & Co. Smelter (site # 214, fig. 2), which could 

reduce the sulfide lead-silver ores to metallic bullion, opened 

in Silverton in 1875. This stimulated production by providing a local market for the ores, which avoided expensive and 

difficult transportation out of the basin either by mule train 

or by wagon. However, the smelter operated only intermittently and was dismantled and moved to Durango in 1880, 

where deposits of needed coal and limestone flux were 

located (Ransome, 1901, p. 20). The anticipated completion 

of the Denver & Rio Grande Railway’s San Juan Extension 

also influenced the smelter’s move. The railroad arrived in 

Durango in July 1881 and in Silverton in July 1882 (table 4). 

Mining production increased dramatically as reduced transportation costs for both ores and supplies stimulated development 

(Ransome, 1901). Ores were shipped by rail to the San Juan 

and New York Smelter in Durango for processing. In 1899, 

this facility became the American Smelting and Refining Co. 

Table 3. Aerial tramways built in San Juan County.

[Locations, code letters, fig. 2; approximate dates where uncertain]

Name Built Code

Silver Ledge tram c. 1890 A

Henrietta tram c. 1905 B

Mogul tram 1900 C

Gold King tram 1899 D

Sunnyside tram c. 1889 E

Sunnyside tram (relocated) 1917 F

Sound Democrat tram 1900 G

Gold Prince tram 1905 H

Kittimack tram c. 1907 I

Hamlet tram c. 1903 J

Ridgeway tram 1946 K

Little Nation tram c. 1928 L

Old Hundred tram 1904 M

Gary Owen tram c. 1925 N

Buffalo Boy tram c. 1926 O

Green Mountain tram 1904 P

Pride of the West (level # 3) tram c. 1910 Q

Little Fanny tram c. 1946 R

Highland Mary tram 1904, 1940 S

North Star tram 1898 T

Contention tram c. 1900 U

Big Giant tram c. 1910 V

Silver Lake #1 and #2 trams c. 1899 W

Royal Tiger tram c. 1890 X

Iowa tram c. 1890 Y

Unity tram c. 1905 Z

Shenandoah-Dives tram 1929 AA

Mayflower tram c. 1915 BB

Little Giant tram 1872 CC

Aspen tram c. 1906 DD

Lackawanna tram c. 1928 EE

Titusville tram c. 1900 FF

Royal Mining Co. tram c. 1905 GG

Detroit tram c. 1900 HH

Champion tram c. 1900 II

metal prices or wars, only to close when prices dropped or 

Federal Government price supports were removed after the 

conflicts. The term “large mine” is relative to the historical 

period. In 1890, “large” was 100–200 short tons per day; 

by 1940, “large” had risen to 600–700 short tons per day.

Purpose and Scope

The purpose of this report is to identify the major historical mining, milling, and ore processing practices, technology, 

economics, and events that influenced mining production in 

San Juan County, Colo., and to place these historical practices 

in context with possible environmental effects in the Animas 

River watershed.

54 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 55

(ASARCO) Smelter in Durango, which was the regional 

smelter for lead-silver and quartz-gold ores and concentrates 

until it closed in 1930 (fig. 6). Rail connection to the smelters was an important component of the economic success of 

mining in Silverton well into the 1950s, when trucks finally 

replaced rail shipping.

As the mines expanded production, mining and oresorting practices continued as just described, but on a larger 

scale. More men were employed in additional working areas 

to achieve this higher production. Larger ore-sorting houses 

were built at the mines. By the end of the period, the larger 

mines were producing over 100 short tons of ore per day from 

tunnels as much as hundreds of feet long with multiple levels 

interconnected by internal and surface shafts.

The Federal Government supported mining development 

in several ways during this period. The General Mining Law 

of 1872 codified the ability to claim and later purchase government land for mining purposes. Purchase of government 

land by individuals and companies was a tenet of government 

policy throughout the late 19th and early 20th century. It was 

one of the primary ways the government raised revenues prior 

to income tax. In 1878, the Bland-Allison Act directly helped 

silver mining by requiring the Federal treasury to purchase 

about 24 million dollars worth of silver a year for minting 

coins for monetary purposes (Brown, 1984).

Milling Development and Practices

Most of the ores mined in the district were lead-silver 

ores (galena and tetrahedrite) that contained minor gold 

and were not very amenable to the mercury amalgamation 

processes used successfully in California and the Comstock 

District in Nevada. For this reason, direct smelting of crude 

ores of the various classes was the normal method of ore 

processing. San Juan County produced little “free milling” 

gold ore, though some gold was present in the Animas district 

ores (Varnes, 1963). According to published data, five stamp 

mills were built in the 1870s and nine were constructed in 

the 1880s (table 1). All were small, ranging in size from 10 

to 70 tons per day capacity. Most included both amalgamation 

and concentration processes. Of the 14 stamp mills, only 

4 are known to have survived into the 1890s; two of these 

were built in 1888 and 1889. The milling processes used during this time could not effectively treat the polymetallic ores 

of the county.

Environmental Aspects

Smelters in this and later periods could not treat ores 

containing more than 10 percent zinc due to metallurgical 

factors (Henderson, 1926). The smelters levied stiff charges 

against the mines for zinc contained in the shipped ore. 

Therefore, miners worked hard to leave the zinc in place in 

the mine, or sorted and cobbed the zinc off by hand. The zinc 

mineral, sphalerite, was disposed in waste dumps at the mine 

and as part of the waste ore used to fill the stopes. This “waste” 

still contained a relatively large amount of metal-bearing 

mineral. Thus, significant sulfide material including sphalerite 

was left where surface and underground water could potentially 

dissolve and mobilize metals, particularly the discarded zinc. 

Both copper and zinc contamination have been identified 

as limiting factors for aquatic life in several sections of the 

Animas River and tributaries (Besser and others, 2001).

The Greene & Co. Smelter (site # 214, fig. 2) and other 

pioneer smelters in the Silverton area operated for a short 

period prior to and during World War I. These smelters were 

tied to the mines by the local narrow gauge railroads (fig. 2 

and table 4) and emitted acid- and metal-bearing flue dusts and 

gases from the oxidation of sulfur in the ores (fig. 7). These 

products were released directly into the environment. The 

stamp mills used the mercury amalgamation process to recover 

native or “free” gold. Industry practice at this time was to discharge mill tailings directly into a nearby creek. Some mercury 

may have been introduced into the environment by these mills 

(table 2).

Total tonnage mined in the period 1874–1889 is 

estimated at 93,527 short tons with most of this having been 

shipped to the smelters (table 1). Thus, only a small amount of 

this production was probably discharged as mill tailings into 

the Animas River watershed.

Table 4. Narrow gauge railroads built in San Juan County.

[Data from Sloan and Skowronski, 1975; locations shown in fig. 2; blank, date uncertain]

Name From To Length 

(mi) Started Completed

Denver & Rio Grande Railway Durango Silverton 45.1 July 1881 July 1882

Silverton Railroad Silverton Red Mountain 11.5 July 1887 Sept. 1888

Red Mountain Ironton 6.0 Fall 1889

Silverton Northern Railroad Silverton Silver Lake Mill #2 (# 219) 2.2 Nov. 1895 Spring 1896

Eureka 4.0 Summer 1896

Animas Forks 3.9 Spring 1904 Nov. 1904

Green Mountain Branch Howardsville Green Mountain Mill (# 240) 1.6 Spring 1905 Fall 1905

Silverton, Gladstone, and Northerly Railroad Silverton Gladstone 7.1 Spring 1899 Sept. 1899
0

100,000

200,000

300,000

400,000

500,000

ORE, IN SHORT TONS

1870 1890 1910 1930 1950 1970 1990

YEAR

Total Production

I II III IV

100

1,000

10,000

100,000

1,000,000

ANNUAL PRODUCTION, IN TROY OUNCES

1870 1890 1910 1930 1950 1970 1990

YEAR

Silver 

Gold 

1

10

100

1,000

10,000

ANNUAL PRODUCTION, IN SHORT TONS

1870 1890 1910 1930 1950 1970 1990

YEAR

Zinc 

Lead 

Copper

56 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 57

Figure 3 (facing page). Historical production for San Juan County, 

1871–1991 (table 1). Total ore production and annual production 

of copper, lead, and zinc are in short tons; gold and silver in troy 

ounces. Periods of production also shown.

Figure 4. Sacking sorted crude ore for shipment to the smelter (Silverton Standard folio, 1904). Early mining was by 

hand methods. Ores were sorted and sacked for shipment to the smelters. Low-grade and sphalerite-containing waste 

was cast aside manually.

Period II—The Gravity Milling Era 

1890–1913

Mining Development and Practices

During this period, mining development greatly expanded 

due to Federal Government supports, stable to rising commodity prices, and improved technologies. In 1890, the Sherman 

Silver Purchase Act was passed by Congress as part of a 

compromise to gain the support of Senators in western mining States for import tariffs desired by Senators from eastern 

manufacturing States. This act required purchase of 54 million 

ounces per year of silver, more than twice what the BlandAllison Act authorized. Colorado silver mining boomed as 

silver prices rose from $0.84 per ounce to as high as $1.50 

(Brown, 1984). New mining technologies were developed 

in this period. First, the wire-rope aerial tramway revolutionized transportation of ore, machinery, and supplies to remote 

mine sites (fig. 8 and table 3). Then, compressed-air powered 

machine-drills increased productivity, resulting in increased 

production. Finally, the application of electricity to many mine 

and mill tasks increased efficiency and throughput to handle 

the increased mine output. The new tramways and mills were 

integrated into the narrow gauge railroad system during this 

period (tables 2 and 3). Three independent rail lines were 

built out of Silverton to serve the new milling facilities, which 

were located adjacent to the railroads (table 4). The railroads 

brought in coal and supplies to service the mines and shipped 

ore concentrate out of the basin to smelters (figs. 6, 9, and 10; 

Sloan and Skowronski, 1975).

In the large mines, tonnages exceeding 200 short tons 

per day became practical, and upward of 400 men could 

work year around at a remote high-altitude site such as 

Silver Lake (mine # 343) or Sunnyside (mine # 116). The 

larger mines had several thousand linear feet of drifts and 

tunnels. Ore sorting in surface houses continued to expand 

as increased mine production yielded lower grade ores. Most 

mines still used cut-and-fill stoping methods, or open “stull” 
Figure 5. Miners working inside a cut-and-fill stope, Gold King (mine # 111; circa 1899, Silverton Standard folio, 1904). 

This rare view inside a stope was staged for promotional purposes, but the photo shows hand drilling on a stope 

hanging wall and ore being cobbed with a hammer while an engineer studies samples. Miners are working off a fill pile 

while timbers support mined-out area above.

(timber-supported) stopes. Milling became the predominant 

ore processing method as the tonnage increased and ore values 

dropped. Several classes of ore were mined and sorted for both 

direct smelting and milling, depending on the grade of the ore. 

During this period near-surface “bonanza ores” were mined 

out, and improved milling technology encouraged mining of 

larger portions of the veins, both of which resulted in lower 

average ore grades. Frederic L. Ransome (1901, p. 24) of the 

U.S. Geological Survey accurately predicted: “It is very probable that the future will see a great and permanent increase in 

the productive development of such large and persistent ore 

bodies of low average grade.”

The development of the wire-rope aerial tramway was 

a unique feature of San Juan County mining (fig. 2), and most 

of the trams in the county were built during this period (table 3). 

These allowed large tonnages of ore to be transported down 

from high-altitude mine portals to mills along the river and the 

narrow gauge railroad system. Crude ore was shipped straight 

through to loading bins on the railroad, while milling-grade ores 

were off-loaded separately into the mill (fig. 10). These trams 

could be as long as 2 or 3 miles in length. Coal, supplies, men, 

and machinery all rode trams to and from the mines; ores were 

shipped down in buckets. By 1907 nineteen tramways totaling 

119,850 linear feet were constructed (Silverton Miner, 1907). 

Both the Iowa (Y, fig. 2) and Sunnyside (E, F, fig. 2) trams were 

each nearly 3 miles in length.

An 1899 report by Edward G. Stoiber, owner of the 

Silver Lake (mine # 343), summarizes the dramatic changes 

made at the mine during this period of property consolidation 

and expansion (Chase, 1952, p. 114):

At the time of the purchase of the property in 1887, 

probably not over 500 ft of work had been done 

on same, and there were but two claims in the 

group; today the underground workings may reach 

a total length of 35,000 ft, and the group embraces 

about 100 claims.***It is claimed for this property 

that it is a low grade concentrating proposition, with 

the premises of practically unlimited vein area to 

draw from.

58 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 59

Economic and political policies affected mining during 

this period. In the face of a mounting financial crisis caused in 

part by the Sherman Act, President Cleveland called a special 

session of Congress to repeal the act in 1893. This financial 

panic precipitated a national economic depression, which 

lasted until 1896 (Brown, 1984). Repeal of the Sherman Act 

caused the price of silver to fall from more than $1.00 per 

troy ounce, its typical value since the 1870s, to an average 

of $0.63 per ounce in 1893. Lead and copper prices also fell 

during the depression, though not as much, and they recovered faster. Silver prices languished throughout the period. 

Marginal mines were closed. Gold prices were supported 

by the Federal Government at $20.67 per ounce as part of 

the monetary Gold Standard, so that mines with significant 

gold content remained open and even expanded. After 1896, 

base-metal prices increased significantly as the U.S. economy 

expanded and many new mine and mill projects were built. 

In 1897, the Colorado Bureau of Mines reported that more 

than 160 mines were operating in San Juan County (Colorado 

Bureau of Mines, 1898). The Financial Panic of 1907 lowered 

metal prices again and greatly reduced the flow of investment 

capital needed for mine expansion. The beginning of World 

War I in 1914 led to a substantial increase in base-metal prices, 

resulting in the reopening of many mines and the expansion 

of others—notably the Sunnyside (mine # 116, fig 1).

Milling Development and Practices

As improved mining technology helped increase production, milling technology also improved to cope with larger 

tonnages of low-grade, metallurgically complex ores. Stamp 

mills utilized mechanically dropped heavy iron rod-like hammers to pulverize the ore (figs. 11 and 12). To extract the gold, 

concentrating machines called “tables” were used to separate 

the various minerals by gravity into “concentrates” containing lead-silver or lead-copper. If the ore contained significant 

gold, mercury-coated copper plates were located after the 

stamps and ahead of the tables to catch the gold particles 

(fig. 12). Various concentrating machines were developed 

and relied on differences in specific gravity to separate the 

mineral particles from worthless rock, hence the term “gravity 

milling.” By 1899, the Wilfley table was established as the 

leader in the field (Niebur, 1986).

Figure 6. Durango Smelter along the Animas River, 1906 (C.A. Chase photo). Silverton lead-silver ores were shipped to the 

smelter in Durango for processing into metal. The process produced considerable air pollution.
3

Ore conditions at the Silver Lake mines, Silverton, Colo., in ShenandoahDives Collection, Center for Southwest Studies, Fort Lewis College, Durango, 

Colo., 15 p. (unpublished).

Figure 7. Kendrick-Gelder (aka Ross) Smelter (site # 213, fig. 2) in Silverton and SG&N Railroad (circa 1907). Silverton 

had several short-lived smelters, connected to the mines by the narrow gauge railroad system. These small plants were 

uneconomic except during periods of high metal prices.

Mills, of which successful ones had been something 

of a rarity in Silverton, now were built at all but the smallest mines (for example, fig. 11). In 1899, the Silver Lake 

Mill # 1 (# 347, fig. 2) concentrator was built on the shore 

of Silver Lake at 12,125 ft elevation (table 2 and fig. 13) 

(Ransome, 1901). This mill was more than twice the size 

of the next largest in the county. The economic advantages 

of milling were significant. Low-grade ores could be concentrated into valuable high-grade concentrates that could 

be smelted more profitably than crude ore. Because smaller 

tonnages of material went to the smelter, both smelting and 

shipping costs were reduced and net revenue increased. 

However, zinc ores were still unmarketable during most of this 

period, because the mills could not efficiently separate it from 

the waste rock and local smelters could not process zinc ores. 

In 1897, twelve mills and two crude ore-purchasing stations 

called “samplers” were reported in operation. The largest 

mills were 200 short tons per day capacity, but most processed around 50 short tons per day. Total daily capacity of 

the crude ore samplers was 200 short tons per day and the 

mills 850 short tons per day in the county. Production was 

not continuous all year at all mills, however, in part because 

of severe weather at the high-elevation mine and mill sites. 

By 1901, additional mills increased combined active production to 1,470 short tons per day; annual production exceeded 

200,000 short tons (table 1; Henderson, 1926). In 1897, six 

of the twelve mills included mercury amalgamation as part of 

the process. One mill used “lixivation,” a sodium thiosulfate 

leaching process, to recover silver (Colorado Bureau of Mines, 

1898).

The interrelationship of ore grades, tonnage produced, 

milling technology, and profitability is well summarized by 

the following excerpts from a February 12, 1913, report on 

the Silver Lake mine (mine # 343) by Lawrence R. Clapp, 

Superintendent.3

 The report was written for the mine’s [now 

corporate] owners, American Smelting and Refining Company 

(ASARCO), who purchased the mine from E.G. Stoiber in 

1901 and owned the smelter in Durango.

60 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 61

The future of the Silver Lake Mines in my opinion, 

lies wholly in the solution of the problem of making this [low grade] material profitable and not in 

the search of better grade ore; the former company 

and Mr. Stoiber before them, both fought a losing 

battle in the attempt to keep their reserves of $9.00 

or $10.00 [per ton] ore in advance of their [mill] 

consumption. In so doing they exposed a very large 

tonnage of lower grade material.*** To make $6.00 

ore profitable, will require a total cost of $4.75 per 

ton and a mill extraction of at least 80%. Neither 

of these are beyond possibility. A $4.75 cost would 

mean a big tonnage, the avoidance of an expensive 

tram, an adequate modern equipment, and a high 

[milling] concentration ratio. [This is] considerably 

more than our present mill is capable of.

The solution recommended by Mr. Clapp was to try a new 

milling technique called “froth-flotation,” which indeed 

was set to revolutionize mineral processing both locally 

and nationally.

Environmental Aspects

As mines and mills increased in size and scope, their 

effect on the environment also increased. Mining techniques 

were similar to those of prior periods, but were larger in scale 

owing to increased mechanization. Waste dumps from the sorting houses became large, some exceeding 50,000 short tons by 

the end of the period. Water drainage became more of an issue 

as longer tunnels intercepted ground water. When shaft mining 

was used, water infiltrating into the mines had to be pumped 

out. In the nearby Red Mountain mining district, acidic water 

was a major problem because it dissolved pumps and piping 

and finally contributed to the closure of the Yankee Girl and 

Guston mines (Ransome, 1901). In most San Juan County 

mines, such highly acidic water appears not to have been a 

major problem. However, water infiltrating the “filled”-type 

stopes and dumps probably became acidic, and it would have 

transported metals to the aquatic environment. By the end of 

the period, many mines were operated through long haulage 

tunnels, which were built at lower elevations to lower costs 

Figure 8. Iowa aerial tram (Y, fig. 2 and table 3) in Arrastra Creek (C.A. Chase Photo 1925). Aerial tramways provided 

the key link between high-altitude mines and the mills and railroads located along the river. The Iowa tram is nearly 

3 miles long and climbed the steep cliff to Arrastra Basin in the background. The Silver Lake tram is out of sight in the 

trees to the left.
Figure 9. Silverton Northern Railroad and the Sunnyside mine’s first “zinc train” (1915). Sunnyside began producing a 

zinc concentrate in 1915, which was shipped to a smelter out of the area. This special narrow gauge train was used to 

transport the powdered concentrate in 25-ton capacity boxcars, about half the size of standard gauge cars.

Figure 10. Silver Lake Mill #2 (site # 219, fig. 2) and tram (W, fig. 2) along the Animas River and Silverton Northern 

Railroad (circa 1904). The mill was built in 1900 and burned in 1906. It was later rebuilt and closed in 1914. The Silver 

Lake Mill #2 integrated tramlines, ore processing, and railroads. Crude ore could travel straight into the rail loading bins 

at far left. Low-grade ores were dumped into the terminal at the top of the mill for concentration. Tailings discharged in 

a flume at the base of the mill building on the right and were piped into the Animas River.

62 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 63

Figure 11. Small mills, such as the Intersection Mill located at the head of Minnie Gulch (fig. 2), became common around 

the beginning of the 20th century. At right is a five-stamp Fraser & Chalmers #56 crusher at Intersection Mill (site # 328, 

fig. 2) built in 1909–1910. A second crusher, a five-stamp Allis Chalmers #77 (at left), was added about 1915 (U.S. Bureau 

of Mines, 1910, 1915). Stamps were powered by steam engine (lower right corner of photo). Concentrates were produced 

using a Wilfley table, the remains of which are in the depression in front of the stamps. Note mine-waste pile adjacent to 

mill (about 100 tons).

and to minimize damage and loss of life from frequent highelevation avalanches. These haulage tunnels served to drain the 

ground water down to that level, leaving upper mine workings 

relatively dry. Some of these haulage tunnels such as Silver 

Lake’s Unity tunnel (site # 294) and Sunnyside’s Terry tunnel 

(site # 120) reached several thousand feet in length.

Increased milling during this period had a serious negative effect on surface-water quality. Mills produced a muddy 

slurry waste product called “tailings.” These mill tailings were 

commonly discharged directly into a nearby stream for disposal (Smith, 1987, p. 117). Sometimes they were discharged 

haphazardly on the ground or riverbanks near the mill, and 

crude impoundments were occasionally constructed (fig. 14). 

Stamp-mill tailings contained both a coarse sand fraction and 

fine particles called “slimes.” Because the ore particles were 

soft, they tended to slime, making efficient recovery using the 

Wilfley table difficult. Recovery using gravity milling methods was 40–60 percent efficient (Bird, 1999). Upon discharge 

of the tailings into a stream, the coarse sands tended to settle 

out closer to the mills, whereas the finer material would stay 

suspended in the stream for long distances, affecting water 

quality as far south as Durango, 45 miles downstream from 

Silverton (Durango Evening Herald, July 18, 1902). Gravity 

mills typically recovered as much as 80 percent of the metals 

in the ore, such as gold, silver, and lead. Zinc, iron pyrite, and 

a portion of the copper were not recoverable by gravity mills 

(Niebur, 1986, p. 134). Thus, significant amounts of metal were 

left in the mill tailings, and particularly in the very fine “slime” 

particles that could be widely distributed into the aquatic and 

riparian environment. The water quality was degraded sufficiently in Durango to require an entirely new reservoir and 

delivery system to be constructed on the Florida River for a 

public water supply, to avoid using water from the tailingsladen Animas River (Durango Democrat, August 1–15 and 

November 18, 1902).

Silverton’s first large concentrating mill was located 

beside Silver Lake and deposited tailings directly into it 

(fig. 15). Ransome (1901, p. 145) commented, “The original 

beauty of this little sheet of water has been marred by mining operations, particularly by a partial filling with tailings 
from the Silver Lake Mill” (mill # 1, site # 347, fig. 2). 

About 500,000 short tons of mill tailings were reported to 

be in Silver Lake by 1903 (figs. 13 and 15; Niebur, 1986). 

Despite a long-held Silverton legend of a “pool of mercury” 

in the lake bottom, no mercury amalgamation was used at 

this mill (Ransome, 1901). Later improvements in milling 

technology resulted in about 400,000 tons of these tailings 

being pumped out of Silver Lake between 1914 and 1919 for 

reprocessing in a new mill built especially for this purpose by 

Arthur R. Wilfley (inventor of the concentrating table of that 

name) and Otto Mears (owner of the Silverton Northern 

Railroad) and located along the Animas River (site # 222, 

figs. 2 and 16). Although more metals were removed from 

the mill tailings, 500 short tons per day of these reprocessed tailing residues were then discharged directly into 

the Animas River near the mouth of Arrastra Creek (Niebur, 

1986).

Chemical reagents were not used in the typical gravity 

concentration mill, although mercury-coated amalgamation 

plates were commonly used. Mercury was lost by physical 

attrition off the plates. Because of the high value of mercury, 

mill operators installed special mercury traps, such as the 

“Black Hills Trap,” canvas tables, and other recovery devices 

prior to tailings discharge to minimize mercury losses (Adams, 

1899). This may help explain why mercury contamination 

has not been generally detected in the watershed (Church 

and others, 1997). Sodium thiosulfate was used in one shortlived “lixivation” mill to dissolve certain silver minerals, this 

being the same chemical as photographic “hypo” developer 

solution.

Total ore tonnage produced during 1890–1913 is estimated at 4.3 million short tons. Based on typical milling practice of the time, a large majority of this tonnage would have 

been discharged as mill tailings directly into surface streams. 

Crude ore shipments decreased dramatically during this period 

as most mines now produced low-grade ores for milling. For 

example, during the period 1909–1913, for which data are 

available, only 29,314 short tons of crude ore was shipped, 

whereas 938,990 short tons, representing 96.97 percent of 

all tonnage produced, was milled (Henderson, 1926). These 

numbers show the importance milling had achieved compared 

to the prior period.

Figure 12. Stamps and mercury amalgamation plates, Old Hundred Mill (site # 238, fig. 2) (Silverton Miner, 1907). Inside 

the mills, heavy iron stamps pounded the ore to sand size, which washed over mercury-coated copper plates to catch 

the coarse gold and thence to concentrating tables.

64 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 65

Figure 13. Silver Lake (mine # 343) and adjacent mines, mill, and mill tailings (Silverton Miner, 1907). The Silver Lake 

Mill # 1 (site # 347, fig. 2) at lower right was the first successful low-grade concentrator in the area. Tailings slowly filled 

the north end of the lake but were later removed. See also figures 15 and 16. The Iowa (mine # 345) is in center on right 

side of lake; Royal Tiger (mine # 348) is on left side of lake.

Period III—The Early Flotation Era 

1914–1935

Mining Development and Practices

World War I in Europe caused the consumption of huge 

quantities of metals. The United States entered the war in 

1917, whereupon an already brisk wartime economy boomed. 

Base-metal prices soared as the war continued to increase 

demand (Henderson, 1926). Improvements in both smelting 

and milling, coupled with wartime demand, made zinc ores a 

marketable commodity for the first time (Bird, 1986). Mines 

with zinc, such as the Sunnyside (mine # 116) expanded, 

whereas those without, such as the Silver Lake (mine # 343), 

closed.

The new froth-flotation milling process could do much 

of the separation formerly done by hand sorting and selective mining of ores and could recover zinc. Mining practices 

began a major shift to larger scale “bulk” mining methods 

and away from more selective lower tonnage methods. A 

new mining method called “shrinkage stoping” was developed. 

Here the entire vein was mined, instead of only the richest 

part (fig. 17). When the stope was completed, all the broken 

ore was removed from the mine, leaving a large void. In the 

“cut-and-fill” stope, the void was backfilled with low-grade 

ore or waste rock. With shrink stopes, no ore sorting was done 

and all mined rock was milled. Average ore grade decreased, 

but so did the cost per ton of mining and milling. This was to 

become the dominant underground mining method throughout 

the 20th century in San Juan County.

Other technological changes contributed to this increase 

in tonnage. Larger, more efficient compressed air drills 

replaced the early types. “Wet” drills, also known as Leyner 

drills, increased productivity by reducing dust and improving 

working conditions for the miners (fig. 17). Mines continued to increase in length, depth, and vertical extent. In 1916, 

Sunnyside (mine # 116) became the largest ore producer in the 
county. By 1917, its daily production increased to 500 short 

tons. In 1918, 600 short tons per day was reached and, by 

1928, daily production exceeded 1,000 short tons per day 

(USBM, 1928). Wartime prices also saw many smaller mines 

open, and the old Kendrick-Gelder Smelter (# 213, fig. 2) was 

reopened to treat pyritic copper ores from the Red Mountain 

district (fig. 7; USBM, 1918).

The high metal prices caused by the war were unsustainable, and in 1921–1922, a sharp postwar recession hit 

the Nation. Mining activity in Silverton collapsed. In 1921, 

the county’s total production was a mere 1,100 short tons, 

whereas in 1920 more than 200,000 short tons of ore had 

been produced (Henderson, 1926). Mining recovered in 

1923 with the reopening of the Sunnyside (mine # 116), but 

the character of the mining industry had changed permanently. 

Many small and medium-sized mines closed, some permanently, along with some older large mines such as the Silver 

Lake (mine # 343) in 1921 and Gold King (mine # 111) in 

1925. By the late 1920s, some new mines were opened as 

the national economy grew, notably the Shenandoah-Dives 

(mine # 355), Buffalo Boy (mine # 325), and Little Nation 

(mine # 228, fig. 1). But metal prices again collapsed with 

the onset of the Great Depression in 1930, and only two 

mines sustained any continuous production for the next 

61 years. Small mines played a decidedly secondary role. 

The Sunnyside (mine # 116) closed in September 1930 

leaving the 3-year-old Shenandoah-Dives (mine # 355) as 

the only major producer in the district for the next 23 years 

(Chase, 1952).

Milling Development and Practices

Ball mill grinding and froth flotation for concentrating ores revolutionized mining in the decade of 1910–1920 

(Rickard, 1932). The impact of this new technology was 

dramatic. Instead of coarsely pulverizing ores with crude 

stamps, high capacity wet grinding with steel balls in a rotating drum ball mill created a more uniform and finer product. 

Early flotation used bubbles in an acidified pine-oil and water 

mixture to float off and separate the valuable mineral particles 

from the worthless quartz (fig. 18). More importantly for 

Figure 14. Gold King Mill (site # 94, fig. 2) at Gladstone and SG&N Railroad (circa 1903). Tailings from the Gold King 

Mill can be seen crudely impounded by log dams along Cement Creek. The aerial tram (D, fig. 2) entered the building 

from the upper right; boxcars for concentrate shipment waited along the railroad sidings.

66 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 67

Silverton, the process could separate zinc (sphalerite) from 

the lead and copper sulfide minerals, and worked well on the 

small-particle-sized “slimes” that were not amenable to gravity concentration. In addition, new smelting processes made 

the zinc concentrates produced by flotation marketable at 

last (Rickard, 1932).

The “remarkable success” of flotation on copper ores 

was noted in 1913 by Superintendent Clapp, who did his 

own laboratory experiments on Silver Lake ore (unpublished report in Shenandoah-Dives collection, Center for 

Southwest Studies, Fort Lewis College, Durango, Colo.). 

The first large-scale mills for lead-zinc ores were built at 

Butte, Mont., in 1914, using the patented Minerals Separation 

Syndicate process (Rickard, 1932; fig. 18). Stamp mills and 

Wilfley tables quickly became obsolete for primary milling 

of base-metal ores. The Silver Lake Mill # 2 (site # 219) and 

Gold King Mill (site # 94) in Silverton (fig. 2) added full-sized 

Minerals Separation flotation sections in 1914 with Sunnyside 

Mill # 2 (site # 165) following in 1915 (Henderson, 1926). 

Even the famed table inventor A.R. Wilfley installed flotation 

in his tailings reprocessing mill (site # 222, fig. 2) in 1916 

(Niebur, 1986). The process worked so well that the Terry 

family, long-time owners of the Sunnyside (mine # 116), 

sold their controlling interest in the mine to the U.S. Smelting 

Refining and Mining Company. This large corporation 

had the financial resources to build a huge state-of-the-art 

600 short ton per day flotation mill at Eureka in 1917–1918 

(site # 164, figs. 2 and 19). The new mill recovered as much 

as 90 percent of the valuable minerals, including sphalerite 

as a separate zinc-rich concentrate. The mill tailings now had 

less metal in them, but were finer in size, and the tonnage 

produced increased to 1,000 short tons per day in the late 

1920s. Wilfley tables still used in the new Sunnyside Flotation 

Mill at Eureka (site # 164) were relegated to the minor role 

of breaking down froth on flotation concentrates (Taggart, 

1927). The new mill was the first large lead-zinc flotation mill 

in the State (Bunyak, 1998). Remaining gravity/stamp mills 

in the district became obsolete and when closed by the 1921 

recession, never reopened. Most were burned to recover scrap 

iron during World War II.

Environmental Aspects

In the mines the trend continued toward larger and more 

extensive workings, with more potential impact on groundwater hydrology. Very long haulage tunnels such as the Gold 

King Mill level tunnel (later known as the American tunnel, 

site # 96) and the Frisco tunnel (site # 19) were nearly a mile 

Figure 15. Silver Lake Mill # 1 (site # 347, fig. 2) discharging tailings into Silver Lake (Silverton Standard folio, 1904). 

The tailing flume from the mill is discharging tailings onto the sand pile now filling Silver Lake (see fig. 13). The large 

building is the miners’ bunkhouse.
in length (fig. 1). Significant localized drainage of ground 

water from the mine workings now had considerable potential 

for discharge of acid or metals into the creeks that was not 

documented at the time. Improved milling had some indirect 

benefits during the period. Low-grade and zinc-bearing ores 

were no longer left in stopes or on mine-waste dumps where 

they could come in contact with the environment. Instead these 

ores were processed and much of the galena and sphalerite 

was removed. However, some of the galena, sphalerite, and 

most of the pyrite in the original ore were discharged into the 

environment as mill tailings.

Flotation milling adversely impacted the Animas River, 

compared to earlier stamp milling (Vincent and Elliott, this 

volume, Chapter E22). Ball-milled tailings were much finer 

than stamp mill tailings. Although the mill tailings contained 

less metal per ton, milled tonnage increased dramatically, 

yielding a net increase in the amount of tailings being deposited in the streams. In 1926, Sunnyside’s Flotation Mill tailings (south of site # 164, fig. 2; Church, Fey, and Unruh, this 

volume, Chapter E12, fig. 4, locality B19; Vincent and Elliott, 

this volume) were reported to contain 0.015 oz/ton gold, 

1.0 oz/ton silver, 0.6 percent lead, 0.08–0.13 percent copper, 

and 0.8–1.1 percent zinc (Taggart, 1927).

The finer tailings traveled farther, and their presence 

began to elicit serious, formal complaints from downstream 

water users. In the late 1920s, Durango ditch companies 

sued the Sunnyside mine’s owner, U.S. Smelting Refining 

and Mining Company, over the pollution originating 

from the Sunnyside Flotation Mill at Eureka (site # 164, 

fig. 2 and fig. 19).4

 The main issue alleged was suspended 

material that clogged irrigation ditches rather than any concern about possible metal contamination. Whether the case 

was actually tried is unknown, but the company prepared a 

vigorous defense. It hired Durango assayer Albert P. Root 

to take weekly samples of the Animas River for clarity 

comparisons in Durango from March through September 

1930, when the mine and mill closed. These samples were 

stored under seal for the next 2 years as legal wrangling continued. Root’s field notes survive, and the Animas River was 

typically described as “gray and turbid” during normal and 

low-flow periods. During high flow, the tailings’ gray color 

was obscured by natural sediment (A.P. Root, unpub. field 

4

1931–1932 correspondence of U.S. Smelting Refining and Mining 

Company with A.P. Root, Root and Norton Assayers; author’s collection.

Figure 16. Silver Lake in 1978 showing that early tailings had been removed. Improved milling and pumping 

technology resulted in much of the Silver Lake tailings being removed leaving a circular “crater” where the 

sands once were piled (see fig. 13).

68 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 69

notes, 1930). Mining companies at the time typically argued 

that these sediments were not harmful to fish or agriculture, 

but the attitudes of the courts and the public were changing. 

The mining companies had successfully rebuffed similar complaints 25 years earlier, but now, legal action was being taken 

against them (Smith, 1987).

The oil flotation process used various chemical compounds, but the amounts released were not monitored at the 

time. In the early Minerals Separation Syndicate process, 

the mill water was acidified with dilute sulfuric acid and 

pine oil was added as the frothing reagent. The Mayflower 

Mill (site # 221, fig. 2) used this pine oil process for the first 

few years of operation (figs. 2, 18, and 20). Precisely what 

the Sunnyside Mill at Eureka (site # 164, fig. 2) used in the 

1918–1925 period is unknown, but lead-zinc mill practice at 

the time used alkaline rather than acidic solutions. The 1926 

mill circuit and reagents are described in detail in Taggart 

(1927). Reagents included small amounts of coal tar, creosote, 

naphthalene, pine oil, and potassium xanthate as the main 

frothing reagents. Large amounts of sodium carbonate (soda 

ash) were used to make the mill pulps and solutions alkaline. 

The xanthate chemicals, as an alcohol-like liquid, were 

patented in 1925 and became the basis of modern flotation 

processes. They completely supplanted oil flotation within a 

few years of their introduction (Rickard, 1932). Because no 

State or Federal regulations on chemical discharges existed, 

chemicals used in the mill water were likely discharged with 

the tailings.

In contrast to districts such as Telluride and Cripple 

Creek, there is no record of direct use of cyanide for recovery of gold in San Juan County, probably because of its 

chemical incompatibility with the zinc and copper sulfides 

associated with gold in the ores. Cyanide was used in small 

amounts as a pyrite depressant in flotation beginning in the 

1930s.

Total tonnage produced from 1914 to 1935 was reported 

as 4.2 million short tons of ore with only 36,232 short tons 

reported as being shipped directly to the smelter. Nearly all 

production during this period was milled. Judging from tailings disposal practices of the time, most tailings were deposited into the Animas River and tributaries (Vincent and Elliott, 

this volume).

Figure 17. Shrink stope mining in Shenandoah-Dives (mine # 355, 1937; C.A. Chase photo). Air drills increased productivity 

and size of the mines. Here a Leyner type drill is working a flat-lying stope. In the shrinkage method, the miners stand on the

ore pile which is later completely removed for processing, leaving a void. Vein exposed is about 3 ft thick.
Period IV—The Modern Flotation Era 

1936–1991

Mining Development and Practices

The Great Depression was a very difficult time for the 

base-metal mining industry. Declining industrial production saw the lowest nominal prices of the century for silver, 

lead, copper, and zinc. Gold was an exception: the government devalued the dollar in 1934 by raising the price of 

gold 75 percent from its long-time $20.67 per ounce level 

to $35.00 per ounce (USBM, 1934). This new price support 

sparked a renewed interest in gold exploration, but it had no 

significant effect on production in San Juan County, because 

of the scarcity of gold ore in the area. It did help to keep the 

Shenandoah-Dives (mine # 355), with low-grade gold ore, 

operating through the Depression. The Federal Government’s 

new involvement in the mining business through New Deal 

programs generally helped mining, but at the expense of 

increased regulation (Smith, 1987).

The Shenandoah-Dives Mining Company survived the 

Depression by increasing tonnage mined to reduce per ton 

unit costs, and by improving the efficiency of the Mayflower 

Mill (site # 221, fig. 2 and fig. 20). Starting at 300 short tons 

per day in 1930, the Shenandoah-Dives (mine # 355, fig. 1) 

soon changed from cut-and-fill mining to large shrinkage 

stope mining methods and increased production to 600 short 

tons per day. Virtually every ton of rock broken underground 

was milled. As base-metal prices slowly recovered in the late 

1930s, a few small high-grade lead-zinc mines were developed 

in the district, such as the Pride of the West (mine # 319), 

which, in 1940, built its own 50 (later 90) short tons per day 

capacity mill (site # 227, fig. 2) at Howardsville (Denver 

Equipment Company, 1947). The size and extent of the mines 

continued to increase. The Shenandoah-Dives (mine # 355) 

reached a vertical extent of more than 2,500 ft by 1941, and 

a horizontal extent exceeding 7,600 ft by 1948 (fig. 21; Chase, 

1952).

The Sunnyside (mine # 116) reopened for 10 months 

in 1937–1938, due to a surge in metal prices, but closed due 

to sagging metal prices, high operating costs, and “excessive water which forced the***owners to abandon the work” 

Figure 18. Minerals Separation flotation cells, Mayflower Mill, 1930 (site # 221, fig. 2; C.A. Chase photo). The flotation 

process created froth, which floated the ore particles out of the redwood cells or tanks. The Minerals Separation 

Syndicate was the leading patent holder in the early years.

70 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 71

Figure 19. New Sunnyside Eureka Flotation Mill (site # 164, fig. 2), a large flotation mill built at Eureka, Colo. (circa 

1925, SJCHS collection). The new 600 ton/day (later 1,000 ton/day) Sunnyside Eureka Mill dwarfs the original 150 ton/day 

concentrator (Sunnyside Mill # 2, site # 165, fig. 2) built in 1899, graphically showing the dramatic increase in size 

and scope of later milling operations.

(Standard Metals Corp., 1961). World War II began to affect 

the mining industry. When the United States entered the war 

after Pearl Harbor, there was a severe shortage of zinc and 

other base metals. In 1942, the Federal Government closed 

all gold mines so that scarce mining labor and resources 

could be focused on base-metal production. At that time the 

Shenandoah-Dives (mine # 355), a nominal gold mine, was 

ordered closed by the War Production Board (WPB). Silverton 

mining leaders put political pressure on the WPB through 

Colorado’s governor and congressional delegation. The WPB 

actually rewrote its national regulations to permit ShenandoahDives to meet new criteria and avoid the closure order (Chase 

and Kentro, 1942). The mine and Silverton were revived, 

which incidentally helped save the Durango to Silverton narrow gauge railroad for its future as a tourist line. The remaining equipment and track of the other small narrow gauge lines 

around Silverton were purchased by the U.S. Army for use in 

Alaska during construction of the Alaskan Highway (Sloan 

and Skowronski, 1975).

As flotation milling technology improved and wartime 

demand for metals increased, Shenandoah-Dives and other 

mines began to remine old underground stope fills and surface 

dumps left by previous mine operators. By 1952 ShenandoahDives Mining Company reported recovering 117,238 tons of 

dump from Dives Basin, 80,158 tons of pre-1925 underground 

stope fills, and 29,597 tons from “other sources” (fig. 22). 

Such “dump recovery” was widespread in the county during 

World War II and the Korean War. Government policy further 

stimulated mining and recovery of material from old minewaste dumps when it began to pay bonus price subsidies called 

“premiums” for every pound of metal recovered. Begun in 

February 1942, the Government’s Metals Reserve Company 

paid premiums for every pound produced above a quota 

based upon 1941 production. Lead and zinc premiums were 

2.75 cents/pound, whereas copper received 5 cents/pound. In 

mid-1943, these premiums were increased to 6.50 cents/pound 

for lead, 8.25 cents/pound for zinc and 11.775 cents/pound 

for copper. Premiums were paid at varying levels through 

June 1947, when the plan expired (USBM, 1942, 1943, 1947).

Road building and mineral exploration were also subsidized by the U.S. Bureau of Mines through the Defense 

Minerals Exploration Act (DMEA) and later through the 

Office of Mineral Exploration (OME). The Reconstruction 

Finance Corporation (RFC) actively loaned money for mining 
projects, and the Metals Reserve Corporation bought metals 

and ores directly for Government strategic metals stockpiles. 

Some of these programs survived into the early 1960s (USBM, 

1960).

With such favorable economic and Federal Government 

policies, operators reopened many dormant mines. Ore was 

shipped to Shenandoah-Dives’ Mayflower Mill (site # 221, 

fig. 2) for custom processing, and when its capacity was 

reached, the ore was shipped by rail to the Golden Cycle 

Mill in Colorado Springs, Colo. Many of these reopened 

mines were small, often mining only a few short tons per day. 

Shenandoah-Dives (mine # 355) remained the main producer 

at 600 short tons per day; about 100 short tons per day of 

“custom ore” were being milled (Mayflower Mill, site # 221, 

fig. 2) in summer months for the small mines. The Pride of 

the West (mine # 319), Highland Mary (mine # 359), and 

Lead Carbonate (mine # 106) built or expanded their own 

small mills (sites # 233, # 502, and # 95 respectively, fig. 2) 

and increased production during the war. Production would 

have increased more during the war, except for the shortage 

of labor. Anecdotal evidence suggests that this labor shortage was the main reason the Sunnyside (mine # 116) never 

reopened during World War II, despite large zinc reserves.

The Shenandoah-Dives Mining Company continued 

steady development of its property (mine # 355) and the 

adjacent Silver Lake (mine # 343), which it leased, into the 

early 1950s. Metals prices increased in 1951 in response to the 

Korean War, but they declined after the 1952 election because 

of a perception that President Eisenhower would soon end the 

conflict. In 1953, the new Congress withdrew Korean War 

price supports for lead and zinc. Production at ShenandoahDives ceased on March 17, 1953, which also caused most of 

the remaining small mines dependent on the Mayflower Mill 

to close. A Government DMEA exploration grant kept the 

Shenandoah-Dives Mining Company going for a few more 

years, though without any production.5

 The company later 

became the Marcy-Shenandoah Corporation, which obtained 

key leases on the Gold King Mill level tunnel (site # 96) at 

Gladstone and the Sunnyside (mine # 116) in 1958.

In 1959 a new company, Standard Uranium Corporation, 

formed a joint venture with Marcy-Shenandoah Corporation to 

reopen the Sunnyside mine by building a new lower haulage 

5

Memorandum of C.A. Chase, June 29, 1953, in C.A. Chase Collection, 

San Juan County Historical Society Archives, Silverton, Colo.

Figure 20. Mayflower Mill (site # 221) and reclaimed tailings (sites # 507–510, fig. 2; 2002). Also known as the 

Shenandoah-Dives Mill, it operated for over 60 years (1930–1991). The aerial tram (AA, fig. 2) entered the plant 

at far right while tailings were stacked in tailings ponds on the left (# 507–510). These tailings were capped 

and seeded during 1990s reclamation work by Sunnyside Gold Corp. In 2001 the mill was designated a National 

Historic Landmark by the Secretary of the Interior.

72 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 73 Figure 21. Cross section of Shenandoah-Dives mine in 1950 (Chase, 1952). This cross section view of the Shenandoah-Dives (mine # 355) shows 1880–1925 mined-out areas in black and 1926–1950 stoped areas in shaded gray diagonal lines. The figure graphically shows the difference in size and extent of the mined area removed during the latter “modern” period, when air drills and power equipment were used, relative to that achieved using earlier hand methods. Map shows mining over a vertical extent of 2,500 ft and horizontal extent of 7,600 ft.
Figure 22. 1940s dump reclamation on Shenandoah-Dives vein, Dives Basin, 

photographed in 1978. Dumps left by early hand sorting operations were often reclaimed 

by later innovative methods. This is the North Star mine dump in Dives Basin (mine # 350, 

fig. 1), which was scraped into a shaft of the Shenandoah-Dives mine for transport 

through the tunnel and aerial tram system to the Mayflower Mill (site # 221, fig. 2) three 

miles away and 3,000 ft lower. Snow patch in center of photo is approximately 150 ft in 

length.

74 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 75

tunnel (mine # 96). In 1960, Standard Uranium Corporation 

changed its name to Standard Metals Corporation, bought 

out Marcy-Shenandoah Corporation’s interest, and became 

sole owner of the former Shenandoah-Dives (mine # 355) and 

the Mayflower Mill (# 221, fig. 2). Work began to widen and 

extend the old Gold King Mill level tunnel (site # 96, prior to 

1960) at Gladstone another mile under the Sunnyside mine 

workings. The goal was to avoid the costly hoisting and tramway operations of the former operators, whose main shaft was 

located beside Lake Emma at 12,300 ft (fig. 23). The renovated and extended haulage tunnel was renamed the American 

tunnel. The work is described in the 1960 Standard Metals 

Corporation Annual Report (p. 3):

The [American] Tunnel was driven in order to 

provide an economical means for removal of ore 

as well as drainage. The original schedule for 

reaching the Washington vein was January 1961. 

This has been accomplished in spite of a water 

flow of 3,000 gallons per minute encountered 

from the 9,000 foot mark. *** Prior to driving the 

American Tunnel, the drainage of eight million 

gallons of water in the Sunnyside mine workings 

was *** a potential major problem. Fortunately the 

tunnel intersected a fault zone with fissures resulting in a gradual drainage of the old workings. The 

water level has been dropping an average of more 

than three ft per day in the old Washington Incline 

[shaft]. At this rate, when the raise is ready for the 

breakthrough the volume of water remaining in the 

upper level will be negligible.

The American tunnel (mine # 96) was successful at draining 

the workings, but the new mine drainage flowing into Cement 

Creek would later become a substantial problem when waterquality standards were enacted in the 1970s. Production 

from the Sunnyside (mine # 116) through the 11,000-ft long 

haulage tunnel (mine # 96) began in August 1962, and continued at 700 short tons per day, increasing to 1,000 short tons 

per day for a few years in the late 1970s. Unexpected gold 

discoveries in the early 1970s kept the Sunnyside (mine # 116) 

going long after other similar base-metal mines in Colorado 

had closed.

Other than Sunnyside (mine # 116), only a few small 

mines produced ore intermittently after 1953, usually in 

conjunction with the Pride of the West Mill (site # 233, 

fig. 2) in Howardsville. In 1967, a Texas oil company, the 

Dixilyn Corporation, began a large mineral exploration and 

development project at the Old Hundred (mine # 239). It 

found little ore, but constructed more than 15,000 linear feet 

of new tunnels and expanded the Pride of the West Mill [# 4] 

(site # 233, fig. 2) to 400 short tons per day capacity. Mill 

Figure 23. Lake Emma and Sunnyside mine from Hanson Peak (circa 1940; H.H. Mellus photo, SJCHS collection). The 

original Sunnyside mine (mine # 116, fig. 1) was located at 12,300 ft on the shore of Lake Emma, which was dammed to 

provide water to mills downstream. Men lived in the building complex; snow sheds connected them to the tunnels and 

shafts.
tailings are impounded in a permitted repository at the site 

(site # 234, fig. 2). High gold and silver prices in the late 

1970s and early 1980s caused another increase in mineral 

exploration activity around Silverton. A few new access tunnels were built, but again, little ore was developed or produced. About 40,000 short tons of mostly waste dump material 

was processed at the Pride of the West Mill (site # 233, fig. 2) 

between 1970 and 1990, mainly during periods of high metal 

prices. Several old mines were explored, but gold and silver 

prices did not maintain a high level long enough to sustain 

large-scale new mine development. Sustained mining continued to be confined to the Sunnyside (mine # 116), which 

benefited from both high gold prices and high gold content 

in the ore. Sunnyside also recovered and milled mine-waste 

dumps from the original Sunnyside workings at Lake Emma 

in the late 1980s (figs. 1 and 2).

In the late 1970s, new surface reclamation laws in 

Colorado began to affect ongoing mining operations. In 

1983, aggressive legal action under the Federal Superfund law 

against Newmont Mining’s nearby Idarado mine in Telluride, 

Colo., coupled with declining gold and silver prices, caused 

all major United States and Canadian mining companies 

then exploring in San Juan County to soon terminate leases 

and exploration activities. After 1984, no major U.S. mining company initiated any new exploration activity in 

San Juan County. The continued exception was the Sunnyside 

(mine # 116), which developed into the State’s largest gold 

producer in the 1970s. However, its operator, Standard Metals 

Corporation, went bankrupt in 1984, closing the mine. Its 

troubles began in 1978 with the flooding of the mine by Lake 

Emma. This precipitated a corporate takeover fight, and the 

ensuing debt load and subsequent fall in gold prices bankrupted 

the company. In November 1985 the mine and the Mayflower 

Mill were purchased by Echo Bay Mines and reopened as 

Sunnyside Gold Corporation in early 1986. By August 1991, 

the mine’s higher grade gold ore reserves were exhausted, 

base-metal prices were falling, and the mine closed except 

for reclamation work, which continued for 12 more years. 

Low metal prices, coupled with increased expenses related 

to complex environmental regulations, resulted in a cessation 

of mining and exploration activity in the county after 1991, 

following a pattern similar to that of other mining districts 

in Colorado. Since 1991, no ore production has occurred 

in San Juan County, after 121 years of continuous mining 

production.

Milling Development and Practices

In the 1930s, the Mayflower Mill was the only milling 

operation in the upper Animas River basin. As a result of both 

downstream complaints and the personal philosophy of management, the first successful steps were taken to prevent water 

contamination caused by mill tailings. When the Mayflower 

Mill (site # 221, fig. 2) was built in 1929, Shenandoah-Dives’ 

manager, Charles A. Chase, with the support of concerned 

stockholders, intended not to discharge mill tailings into the 

Animas River at all. Instead, special tanks and machinery 

were installed to settle the mill tailings and haul the sand 

back up the tramline, where it would be dumped as a surface 

pile, thereby keeping it out of the Animas River. Mill water 

would be filtered and recycled. Unfortunately the equipment 

did not work, and being in financial difficulty because of the 

Great Depression, the company discharged mill tailings into 

the Animas River as mills had before (Smith, 1987). In 1935, 

Chase received recommendations for a tailings impoundment 

built from its own sand that was being used in Butte, Mont. 

under operating conditions similar to those at Silverton. The 

technique relied on the fact “***that a single spigot will draw 

off sand in such a ratio to water as will permit the sand to build 

in a firm pile; and of course a series of such piles will merge 

into a continuous wall of sand” (fig. 24; Chase and Kentro, 

1938, p. 19).

By 1936, nearly all Shenandoah-Dives mill tailings 

were being retained in sand-walled ponds (site # 507, fig. 2), 

keeping them out of the Animas River (fig. 25). The slimes 

and fine suspended material settled out in the pond formed 

behind the sand wall. As the water cleared, it was decanted 

out of the pond through wooden culverts (called decants) 

buried under the sand wall, and thence into the Animas River. 

When Sunnyside (mine # 116) briefly reopened their Eureka 

Mill in 1937–1938 (# 164, fig. 2), it too built settling ponds 

in the Animas River valley below Eureka (Church, Fey, and 

Unruh, this volume, fig. 4, locality B19; Vincent and Elliott, 

this volume). Variations of this method and improvements on 

it were used by all mills operating after 1935, until the end of 

milling in 1991 (site # 507–510, fig. 2).

Although this method of transport and emplacement 

of tailings was effective, the settling-pond system designed 

to contain the material was not perfect. The crudely constructed sand walls built on the hillside near the Mayflower 

Mill were plagued by springs, entrained ice, and slimes, 

and were therefore not structurally stable. The sand wall 

on tailings pond # 1 (site # 507, fig. 2) collapsed in 1947 

(fig. 26) and again in 1974. The latter collapse released 

more than 100,000 short tons of tailings into Boulder 

Gulch and the Animas River and resulted in abandonment of the pond (site # 507, fig. 2; Bird, 1986). In 1947, 

the accident resulted in no legal actions against the company. The settling pond wall was promptly repaired, and 

the company even received a commendation for its pollution control efforts from the Colorado Fish and Game 

Department. By 1974, however, the story was different. 

Standard Metals Corp. was fined $40,000 (later reduced 

to $15,000) for contaminating the Animas River. Active 

water-quality monitoring of the mill tailings decant water 

became standard practice about 1977, with the advent of the 

National Pollution Discharge Elimination System (NPDES) 

permitting system.

76 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 77

From 1935 to 1991 milling technology gradually 

improved in efficiency but remained similar in method and 

operations. Metal recovery was often as high as 95 percent 

by the 1940s, and only incremental improvements were made 

into the 1970s. The one large change was the abandonment 

in the mid-1930s of the old oil flotation chemistry at the 

Mayflower Mill (site # 221, fig. 2), replaced by more efficient xanthate flotation reagents for the separation of a zinc 

concentrate. Tailings ponds also improved with the use of 

hydro-cyclone type classifiers replacing wooden launders, 

sluices, and spigots for dam construction. In its 1965 annual 

report, Standard Metals (1966, p. 7) noted, “Tailing disposal systems were improved in line with current stream and 

river pollution regulations and practices.” This is an example 

of Colorado’s efforts at water-quality regulations prior to 

national legislation.

During the period 1936–1991, a reported 9.5 million short 

tons of ore was mined and milled with all but an estimated 

200,000 tons of mill tailings being impounded in settling ponds. 

Crude ore shipments for the period 1936–1957 amounted to 

only 8,148 tons.

Environmental Aspects

Changing public attitudes and government philosophy 

resulted in new legislation and legal proceedings in both the 

1930s and 1970s. These changes forced mine operators to 

modify or improve practices to reduce environmental degradation caused by mining and milling (Smith, 1987). Required 

improvements tended to increase operating costs, though 

metals prices continued to decline in both nominal and real 

terms. The number of operating mines markedly decreased after 

1953 as mining economics became less favorable. Underground 

mining practices continued much as in the past, but longer 

haulage tunnels at lower elevations increased mine drainage 

discharges, as at the Sunnyside (American tunnel, mine # 96), 

and Old Hundred (mine # 239).

Wartime demand and Federal Government policy in 

the 1940s and 1950s resulted in significant road building, 

processing of old mine-waste dumps, and reopening of old 

mines. Little regard was paid to the condition of the surface after such war-inspired activity. Most old stamp mills 

were burned and their scrap metal salvaged in support of the 

Figure 24. Mill tailings spigots at tailings pond # 1, Mayflower Mill (site # 221, circa 1934; C.A. Chase photo). Wooden 

flumes were used to slurry tailings for disposal into tailings ponds (# 507, fig. 2) rather than into the river. Holes in the 

bottom of the flume let coarser sands flow down the planks into piles, which were shoveled together to create the pond 

wall while water settled behind the resulting dam.
war effort. Underground workings of the larger mines were 

expanded to tens of thousands of linear feet with multiple 

working levels. This resulted in ground water being drained 

from the vicinity of the mine workings and discharged out of 

the lowest haulage tunnel directly into the surface streams. 

Few large surface mine-waste dumps were created during the 

1936–1991 period because most mineralized material was 

milled. The several new access tunnels built did generate large 

mine-waste dumps of mostly unmineralized “country” rock. 

Colorado passed one of the first comprehensive surface reclamation laws in 1976, which required surface disturbances to 

be reclaimed after mining was completed on both private and 

Federal lands.

Key legal actions in the 1930s finally pushed the mining industry to find solutions to the problem of turbid mill 

tailing discharges. In March 1935, the Colorado Supreme 

Court upheld a lower court ruling against the Chain-O-Mines 

Company in the town of Central City and ordered it to cease 

mill tailings discharges into adjacent Clear Creek (Smith, 

1987). Legal action was never taken against ShenandoahDives Mining Co., who instead cooperated with downstream 

farmers and ditch companies to find a solution it could afford. 

Mill tailings settling ponds were begun in July 1935, and by 

June 1936 the majority of the mill tailings produced in the 

Animas River watershed were retained (site # 507, fig. 2). 

According to manager Chase, by August 1937 the system 

achieved “complete retention” of the mill tailings. “Decanted 

water is, for the most part above reproach as to clarity *** The 

Animas is reported a first-class fishing stream.” Still, noting 

new grass growing on the sand wall he wrote, “we may yet 

demonstrate to the farmers that they are deprived of good soil 

building material” (Chase and Kentro, 1938, p. 21). Charles 

Chase was ahead of his time, but he still maintained the 

industry’s long-held belief that the tailings themselves were 

benign or even beneficial.

When the Sunnyside (mine # 116) reopened in 1937, 

mill tailings pond dams were built with mechanical excavators 

on the flat river gravels south of Eureka (south of site # 164, 

fig. 2). After the mine was abandoned and the Sunnyside Mill 

at Eureka was scrapped in 1949, these tailings dams partly 

washed out and some of these tailings entered the Animas River 

(Vincent and Elliott, this volume). Remaining mill tailings 

were removed to the Mayflower tailings pond # 4 repository 

(site # 510, fig. 2) during reclamation activities in the 1990s.

Besides the occasional accident or error, decant water 

quality varied due to a number of factors. Wind and thunderstorms would sometimes stir up the shallow water in the 

settling pond, allowing slimes into the discharge. Close attention by operators was needed to keep the decanted water clear. 

Occasional complaints were registered with the State against 

Figure 25. Tailings pond # 1 sand wall (site # 507) at Mayflower Mill (1936; C.A. Chase photo). As tailings were deposited 

the sand walls became higher. Tall flumes (shown on left of sand wall) called “launders” now were needed to transport 

the sand and water.

78 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 79

Shenandoah-Dives Mining Co. when conditions downstream 

deteriorated—even if the company was not to blame. Smith 

(1987, p. 131) noted, even though Charles Chase’s

enlightened attitude put to shame many of his contemporaries [in the mining industry] *** he discovered growing sentiment against mining’s activities, 

and found his company in the role of the scapegoat, 

simply because Shenandoah-Dives represented 

the largest and most obvious local operation. *** 

Chase’s problems [in Silverton] portended what 

would come on a larger scale.

Chemical and metallic constituents of decant water 

were not regulated until the late 1970s. Beginning in 1937, 

small amounts of cyanide (less than 10 ppm) were used 

in the mill water to depress iron in the flotation process 

(Taggart, 1945). Small amounts of cyanide were used until 

the end of milling in 1991, although in reduced amounts 

followed by treatment in the pond water, as discharge 

regulations became more stringent. Even at the time of the 

closure of the Mayflower Mill in 1991, the biotoxicity of 

various mill reagents was not well understood. Xanthate 

concentrations in mill water discharges were never regulated 

by State or Federal agencies during the period of operation 

of the Mayflower Mill, 1930–1991.

Potential ground-water contamination by mill tailings pond deposits was also not addressed by regulators or 

industry until the 1980s. Settling ponds built in prior years 

were not sealed and infiltration into ground water or nearsurface water is known to have occurred below some ponds 

(Jim Herron, Bruce Stover, and Paul Krabacher, Unpublished 

Lower Animas River reclamation feasibility report, Upper 

Animas River Basin, Colorado Division of Minerals and 

Geology, 2000). This seepage process can result in ground 

water contamination by metals leached from the mill tailings. 

Though none of the older settling ponds were sealed to prevent 

contact with ground water, not all old tailings ponds resulted 

in surface or ground-water contamination. The 1940s tailings 

pond at the Highland Mary (site # 361, fig. 2) is an example. 

Some mill tailings material is chemically neutral or contains 

sufficient alkaline minerals, or the pH of water is sufficiently 

high, that any pyrite contained in the mill tailings will not 

be oxidized (Unpub. Reclamation feasibility report, CDMG, 

2000).

Figure 26. Failure of tailings pond # 1 sand wall dam (site # 507) at Mayflower Mill (1947; C.A. Chase photo). As sand 

walls became higher, structural instabilities also increased. Ice lenses in the wall were partly to blame for this 1947 

collapse. The 1974 wall failure would be just out of this view to the left. Reclaimed tailings are shown in figure 20 to left 

of Mayflower Mill.
One dramatic event did adversely affect the Animas 

River for a short time in 1978. Standard Metals Corp. was 

mining the Spur Vein, a high-grade gold vein in the Sunnyside 

(mine # 116) 85 ft below Lake Emma, located at 12,300 ft 

elevation in Sunnyside basin (fig. 23). About 6:00 p.m. on 

Sunday, June 4, 1978, Lake Emma broke through into the 

2580 Stope on C level, flooding the mine on the only day of 

the week when no miners worked underground (fig. 27). The 

effect on the mine was cataclysmic, stripping timbers from 

the main shaft, crushing equipment, and filling tunnels with 

mud. At the Gladstone portal (mine # 96, fig. 1) an estimated 

5 to 10 million gallons of water blew out the walls of the 

portal building under the pressure of a 1,700-ft head from 

the lake and covered everything with black mud (figs. 28

and 29). Sheriff Virgil Mason, on his way to the Gladstone 

portal, told reporters he saw “a wave that must have been 

eight to ten feet high rushing down the creek. At the portal 

it was like a UFO movie. Everything was black and timbers 

were shooting out like they were shot from a launcher” (Daily 

Sentinel, June 11, 1978). Alongside other townspeople, the 

author, who was employed by Standard Metals as an assayer 

at the time, watched Cement Creek flood. Main shaft timbers 

floated by in the roiling black water, which smelled strongly 

of diesel fuel and sulfides, but the tension of the close call with 

human tragedy outweighed any thoughts of the environmental 

effect of the event being witnessed.

Standard Metals Corp. explained the cause of the accident briefly in its Annual Report issued in May 1979:

Studies of the breakthrough, made on behalf of the 

Company, have indicated that it was caused by a 

fault, filled with glacial till and other gangue material, 

which resulted in substantial amounts of water, mud 

and debris entering the mine, and blocking entrance 

through the tunnels.

Indeed, unknown to the miners and geologists, thousands of 

years before, glaciers had gouged a crack along the weak vein 

rock that was filled with permafrost sediments. Heat from the 

mine melted the frozen mud and Lake Emma drained into the 

stope (R.C. Dwelley, Cripple Creek, Colo., oral commun., 

1985). One of the first mine geologists to examine the hole 

found clear glacial ice embedded in the fault (F.D. Taylor, 

Silverton, Colo., oral commun., 2003).

The Animas River turned black from the glacial mud 

and sediment well past Farmington, N. Mex., more than 

70 mi downstream (fig. 30). (An analysis of the Lake Emma 

Figure 27. Lake Emma after collapse (photo taken June 11, 1978; note man (circled) in photo for scale). Lake Emma 

collapsed into the Sunnyside mine (mine # 116) after permafrost filling a fault on the Spur Vein failed from the heat in 

the mine. The resulting crater is about 300 ft wide, 800 ft long, and as much as 85 ft deep. Glacial mud and debris filled 

much of the mine. Standard Metals Corp. spent nearly 2 years cleaning and repairing the mine before it went back into 

production in January 1980.

80 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 81

sediment discharged is in table 1 of Church, Fey, and Unruh, 

this volume.) The towns of Durango and Aztec had to shut off 

intake of water at their pumping plants to prevent the polluted 

water from entering municipal water systems. Samples taken 

by health officials in Durango showed levels of 12.6 mg/L zinc 

and 4 mg/L lead in the water, and warnings were issued not to 

drink the water (Daily Sentinel, June 11, 1978). At the time of 

the event, most downstream users and the press thought this 

contamination was from mill tailings in Lake Emma. This was 

unlikely because the early Sunnyside mills (sites # 158, 165, 

fig. 2) were built considerably downstream of Lake Emma. 

The first Sunnyside Mill (site # 113) was built at or just below 

the outlet of Lake Emma, which was dammed to provide 

process water to the mill. Photographic evidence suggests the 

mill’s tailings were probably discharged into Eureka Creek. 

Part of the B Level waste dump was deposited in the lake and 

sloughed in further due to the mine collapse. Natural metal 

content of the lake sediments as well as metals washed from 

the mine workings probably accounted for the metal loading. 

Large chunks of ore from the collapsed 2580 stope never made 

it past the Gladstone portal and were recovered and milled 

during the 2-year mine clean-up. Little ore was found in the 

Terry tunnel, the mine’s upper entrance (# 120). Instead, these 

workings were filled with a black sticky mud, similar to that 

observed in the exposed lake bottom. Considerable mud-laden 

water also discharged from this portal, though in a less spectacular fashion, and blackened Eureka Gulch and the Animas 

River between Silverton and Eureka.

Standard Metals Corp. was not fined by any State or 

Federal agency, and the accident was determined to be an “act 

of God” in a Federal court action brought by the mine’s insurance company, which was trying to avoid paying $9,000,000 

in damage claims. Standard Metals Corporation won the suit 

and recovered $5.5 million dollars. The mine resumed production in January 1980 (Bird, 1986). Water drainage was significantly altered in Sunnyside basin, but was largely mitigated 

through reclamation efforts by later mine owner, Sunnyside 

Gold Corp.

Water drainage from long haulage tunnels, such as the 

American tunnel (site # 96, fig. 1), came under regulatory 

and environmental scrutiny when water discharges from mine 

tunnels became closely regulated in the 1970s. Sunnyside 

Gold Corp. has installed hydraulic seals in the principal 

access tunnels to eliminate this drainage. These seals are 

intended to provide a permanent solution to mining’s 100-year 

battle with water and drainage problems, both operational and 

regulatory.

Figure 28. American tunnel portal (mine # 96) June 5, 1978, the day after the Lake Emma flood. Lake Emma water and 

mud discharged at the American tunnel portal at Gladstone some 2,000 ft below and 2 miles away from Lake Emma. 

Black mud was deposited over the dumps and into Cement Creek. Portal buildings are on the site of the Gold King Mill 

(site # 94, fig. 2). Only one small house remains of the town of Gladstone circa 1903 (fig. 14). Photo taken 22 hours after 

the event.
Figure 29. Erosion trench and muddy discharge at American tunnel portal, June 5, 1978, 

the day after Lake Emma flood. With 2,000 ft of head pressure, Lake Emma water exited 

the American tunnel (mine # 96) like a huge fire hose, blowing open the building wall and 

eroding the dump back about 15 ft, creating an erosion trench. The scene was described 

by witnesses as something out of a science fiction movie.

82 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 83

Conclusions

Historical mining and milling practices in San Juan 

County impacted the environment in various ways during the 

121-year period of active mining. These practices in turn, were 

influenced by national and international economics, events, 

industrial policy, public perceptions, and technological trends 

in the mining industry. Knowledge of these historical practices 

can assist us in understanding current environmental issues in 

the Animas River watershed and in developing investigations 

of specific environmental problems that may be related to 

historical practices. Mining and milling practices, particularly 

prior to 1935, tended to release mining wastes directly into 

the aquatic and riparian environment. The magnitude of these 

Figure 30. Crossing muddy waters of Cement Creek, June 5, 1978, the day after Lake Emma flood. The Lake Emma flood 

washed out bridges and blackened Cement Creek and the Animas River for a distance of 70 mi south into New Mexico, 

shutting down municipal water systems along the Animas River.

releases was directly proportional to the level of production 

and number of operating mines and mills. After 1890, technological advances in both mining and milling fostered larger 

scale production averaging more than 200,000 short tons per 

year. The majority of this production was milled, and the 

resultant mill tailings were discharged directly into the watershed until the mid-1930s. Based on reported and estimated 

mine production during the period 1890–1935, an amount 

totaling 8.6 million short tons of mill tailings is estimated to 

have been deposited into the Animas River and various tributaries. This represents 47.5 percent of the total reported and 

estimated mine production of 18.1 million short tons produced 

during the 121-year period of production. These mill tailings 

as well as mine dumps both on the surface and underground 
contain varying amounts of metals unrecoverable at the time 

of their production. Mill tailings entering the watershed often 

affected downstream water users. After tailings retention in 

settling ponds became standard practice in the mid-1930s, 

direct physical contamination of surface waters was nearly 

eliminated. Accidents and operator error did cause occasional 

tailings releases.

Mine workings expanded in length, depth, and vertical extent from the beginning of mining in 1871. As tunnels 

became longer and were constructed at lower elevations, 

mine drainage locally affected ground-water hydrology and 

resulted in point source discharges into the watershed. Earlier 

mining methods left mineralized rock underground in the 

stopes. Later mining methods tended to extract more of the 

mineralized material leaving larger voids and less mineralized 

waste. Fewer surface dumps were created at mine sites when 

improved flotation milling techniques allowed for nearly all 

mined material to be economically milled.

Federal Government policies actively encouraged mining 

until the early 1960s. During wartime direct and indirect financial incentives for increased production and exploration intensified mining activity. Remilling of dumps and stope fills during 

these and other periods of high prices removed some mined 

material from direct contact with ground water at the mine 

sites and transferred it to tailings repositories. Environmental 

regulations enacted in the 1970s required mine operators to 

perform surface reclamation and regulate quality of water discharges from both mines and mills. These regulations increased 

both current and future costs of mining, which, coupled with 

decreased metal prices, effectively ended San Juan County 

mining production in 1991 after 121 years.

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84 Environmental Effects of Historical Mining, Animas River Watershed, Colorado
Mining, Milling, and Production History 85

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Notes on the Table and Chart of Reported 

and Estimated Mine Production

Statistics on total annual mine production were compiled by the U.S. Geological Survey, U.S. Bureau of Mines, 

and State agencies from 1885 through the mid 1970s. Data 

from 1871 to 1900 are recorded in Henderson (1926) but as 

annual dollar value of ores produced, not tons. For purposes 

of constructing figure 3, the tonnage through 1889 is estimated 

by assuming an average value per short ton. For 1890–1900, 

actual average ore values per short ton for 1901 are used 

to back-calculate the tonnage from the dollar figures. For 

1901–1923, production data cited are from Henderson (1926). 

For 1924–1977, production data are from the annual Mineral 

Resources of the United States, later called the Mineral 

Yearbooks of the U.S. Bureau of Mines. However, 1972 and 

1976 are Sunnyside production only from company data. 

For 1978–1991, production data are for the Sunnyside only, 

based on data furnished by Sunnyside Gold Corporation and 

Standard Metals Corporation annual reports; the exception is 

1986, which is from U.S. Bureau of Mines (USBM, 1986). 

An estimate of 20,000 short tons milled by three operators 

at the Pride of the West Mill [# 4] during 1979–1981 is not 

included in the totals, because supporting data are lacking. Metals prices were reported by U.S. Bureau of Mines 

through 1958, except that data from 1924–1931 are from the 

Colorado Yearbook (1932). Metals prices after 1958 are from 

U.S. Geological Survey (1999).

Author Information and Notes on Sources 

of Photographs

William R. Jones (B.A., Economics, Western State 

College, Gunnison, Colo.) is a Professional Registered Assayer 

and present owner of Root and Norton Assayers, Silverton, 

Colo., established 1908. He was an assayer and water analysis 

Appendix

technician for Standard Metals Corporation from 1977 to 

1979. Since 1978 he has been on the Board of Directors of 

the San Juan County Historical Society in Silverton.

Photographs in this report constitute an important source 

of historical information on past mining and milling practices. They come from a variety of published and unpublished 

archival sources in San Juan County, principally the Archive 

maintained by the San Juan County Historical Society in 

Silverton.

Charles A. Chase, General Manager of the ShenandoahDives mine, took numerous detailed photographs of that operation, copies of which were donated to the Society archives by 

his son, Charles H. Chase, of Tucson, Ariz., who was superintendent of the Mayflower Mill 1945–1948. The early halftone 

photographs come from special 1904 and 1907 illustrated editions of Silverton’s pioneer newspapers, the Silverton Standard 

and Silverton Weekly Miner, author’s collection. Color photos 

of the Lake Emma flood were taken by the author.

Photo credits:

Silverton Standard—Illustrated Folio 1904: Figures 4, 5, 

10, 15.

Silverton Weekly Miner—Golden San Juan Edition 1907: 

Figures 7, 12, 13.

Charles A. Chase Collection, Courtesy of the San Juan County 

Historical Society: Figures 6, 8, 17, 18, 21, 24, 25, 26.

Author’s Collection, photographer unknown: Figures 9, 14.

San Juan County Historical Society (SJCHS) Collection, 

photographer unknown: Figure 19; Herbert H. Mellus 

Photo Fig. 23.

William R. Jones Photo: Figures 16, 20, 22, 27, 28, 29, 30.

David L. Fey Photo: Figure 11.

86 Environmental Effects of Historical Mining, Animas River Watershed, Colorado