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This CD contains the page images and searchable text from a 1896 United States Geological Survey report on the gold-bearing formations of the Grass Valley district, in western Nevada County, California. The historic mining districts of Nevada City and Grass Valley comprised a great number of important gold deposits, consisting of both quartz veins and gold-bearing gravels. The mines had been worked continuously between their discovery in 1849 and 1896, producing approximately $113 million. By 1896, hydraulic mining had been largely prohibited, but quartz mining was thriving.
This report by Waldemar Lindgren was published in the Seventeenth Annual Report of the U.S. Geological Survey, and expanded upon his related work: the Geologic Atlas of the United States, Folio #29 - Nevada City Special Folio (also included on this CD) .
Lindgren's report describes the regional geology, presents the mineralization theories of his day, describes the fissure systems and factors which contributed to vein-formation, and characterizes the richness of the free gold versus that fraction found in the sulphides. Lindgren values of the ores of the richer Grass Valley and Banner Hill veins, and the poorer ore of the Nevada City mines. He indicates the width and regularity of the quartz veins, and generalizes on the occurrence and orientation of the pay shoots of high-grade ore.
Over 70 pages are devoted to mine-by-mine descriptions of mine works, yields, and prospects. The 24 appended plates and 37 in-text figures include photographs of quartz and mineral samples, photographs of the mines and of miners at the most important veins, color maps of the workings of the largest mines, black and white maps of the lesser mines, and vertical sections of both. Also included is a Geological Map of Nevada City and Grass Valley Mining Districts, which combines elements of the economic geology and structural section quadrangles found in the Special Folio.
Contents:
CHAPTER 1. Introduction
CHAPTER II. General geology
CHAPTER III. The igneous rocks of the bed-rock series
CHAPTER IV. The igneous rocks of the bed-rock series (continued)
CHAPTER V. The sedimentary rocks of the bed-rock series
CHAPTER VI. Metamorphic processes
CHAPTER VII. The superjacent formations
CHAPTER VIII. Geological history
CHAPTER IX. The ores
CHAPTER X. Changes in the rocks due to fissure and vein formation
CHAPTER XI. Vein structure and pay shoots
CHAPTER XII. The fissure systems
CHAPTER XIII. Genesis of the veins
CHAPTER XIV Detailed descriptions
CHAPTER XV. Detailed descriptions (continued)
CHAPTER XVI. Detailed descriptions (continued)
CHAPTER XVII. Summary
Illustrations:
Plates
I. General map showing location of the special sheets
II. Contour map of the Neocene bed-rock surface
III. Sheeted zone in granodiorite, Main sheet, Grass Valley
IV. Thin sections showing structure of ore
V. Thin sections showing structure of ore
VI. Thin sections showing structure of ore
VII. Specimens showing structure of ore
VIII. Specimens showing structure of ore
IX. Specimen from Merrifield vein showing structure of ore
X. Specimen from Merrifield vein showing structure of ore
XI. Maryland vein on the 1,400-foot level
XII. Maryland vein, stopes above 1,500-foot level
XIII. North Star vein, near 1,700-foot level
XIV. North Star vein, near 1,800-foot level
XV. Ophir Hill vein, Empire mine, near 1,800-foot level
XVI. Bunker Hill vein, Amador County, Cal.
XVII. Ore shoots of Nevada City and Grass Valley mines
XVIII. Ore shoots of Nevada City and Grass Valley mines
XIX. View of Sugar Loaf and Cement Hill from Nevada City
XX. View of Champion and Home mines from Providence mine, looking
down Deer Creek
XXI. Horizontal projection and sections of underground works of the
Providence and adjoining mines
XXII. Map of the new Rocky Bar quartz mine
XXIII. Map of underground works of North Star mine
XXIV. Special map of Nevada City and Grass Valley mining districts.
Figures
1. Section at tunnel 900 feet below Home mine
2. Primary pyrrhotite in augite
3. Intergrowth of primary pyrite, pyrrhotite, and ilmenite
4. Section of superjacent formations at Manzanita mine
5. Bluff at hydraulic cut, near city reservoir, Nevada City
6. Section of breast of workings, West Harmony drift mine
7. Vertical section along West Harmony incline
8. Vertical section along Yosemite incline
9. Section in workings of Odin drift mine
10. Sheeted zone in granodiorite, Deer Creek, Bellefountain mine
11. Vertical section along shaft, Federal Loan vein
12. Vertical section along shaft, Never Sweat vein
13. Vertical section showing faults on the Beckman vein, Mayflower
mine
14. Horizontal projection showing faults on the Floyd vein, Mayflower
mine
15. Vertical section along shaft, Canada Hill vein
16. Horizontal projection showing faults on the Canada Hill vein
17. Woodville vein, North Banner mine, in drift
18. Vertical section along shaft. Pittsburg vein
19. Section of Pittsburg vein, ninth level
20. Map of Oro Fino and other claims
21. Vertical section through St. John shaft
22. Vein in St. John mine, fifth level, 150 feet east of shaft
23. Vein in St. John mine, fifth level, 100 feet west of shaft
24. Cross section of Eureka vein, 300-foot level
25. Cross section of Maryland vein in stopes above 1,500-foot level
26. Cross section of Maryland vein in stopes above 1,500-foot level
27. Vertical section through Eureka shaft, showing veins
28. Approximate outline of the Eureka-Idaho pay shoot
29. Cross section of the Brunswick vein, 700-foot level
30. Longitudinal section, Union Hill mine, showing areas stoped
31. Vertical section along shaft, Omaha vein
32. Longitudinal section, showing fault, Omaha mine, fourteenth level
33. Longitudinal section, old Wisconsin mine, showing areas stoped
34. Vertical section along shaft, Norambagua vein
35. Vertical section along shaft, showing veins and cross fissures, in the
Pennsylvania mine
36. Horizontal projection of contacts on surface and on the plane of the
vein, W. Y. O. D. mine
37. Longitudinal section, showing fault, Ophir Hill vein, twentieth level,
Empire mine
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