Outline of the report.
Introduction.
General geology of the Mother Lode belt.
Geothermal gradient.
Gold ore bodies.
Mineralogy.
Alteration of wall rocks by the ore-forming solutions.
Origin of the gold deposits.
The mines.
Index.

Illustrations:

Plates

Plate 1. Mother Lode belt, as seen from the Central Eureka mine; Mother Lode belt, as seen from summit of Carson Hill
Plate 2. Geologic map of the Mother Lode belt, California
Plate 3. Location of Mother Lode belt and other mining districts with reference to time intrusive rocks of time Sierra Nevada
Plate 4. Ribbon quartz, Plymouth mine; Inclusions of greenstone and black slate in quartz, Original Amador mine
Plate 5. Composite quartz ore from the 4,200-foot level, Argonaut mine; Prominent quartz outcrop at Eagle Shawmut mine
Plate 6. Distribution of gold and structural features of typical quartz vein inclosed in slate, Plymouth mine
Plate 7. Ankerite metasome in slate, ordinary light
Plate 8. Ankerite metasomes in slate, surrounded by fringes of clear ankerite; Metasomatic pyrite in slate surrounded by feather quartz
Plate 9. Geologic map of the area surrounding the Plymouth mine
Plate 10. Ore shoot above the 4,100-foot level, Central Eureka mine
Plate 11. Stereogram of ore shoots of Morgan and Melones mines
Plate 12. Geologic map of the adit level, Eagle Shawmut mine

Figures

Index map showing the location of the Mother Lode belt, California.
Output of Mother Lode counties, 1904-1924.
Geologic map of Mother Lode belt from Plymouth to Jackson.
Structural features of a quartz vein in slate.
Thickness and assay value of ore shoot on the 2,150-foot level, Plymouth mine.
Concentration of gold in the ore shoot on the 2,150-foot level, Plymouth mine.
Section through the Pacific shaft, Plymouth mine.
Ore shoots of Plymouth mine.
Section through Gover shaft, Plymouth mine.
Section through Bunker Hill mine 800 feet north of the shaft.
Section through the main shaft of the Original Amador mine.
Section through the Patton shaft of the Keystone mine .
Section through the shaft of the Central Eureka mine.
Detailed geologic cross section of the lower levels of the Central Eureka mine.
Generalized section through the Kennedy mine along the line of the 1,950-foot crosscut.
Section through the Kennedy vein 280 feet north of the vertical shaft, showing the branching of the vein.
Stope plan of the Kennedy vein on the 3,900-foot level.
Section through the Argonaut shaft.
Geologic map of the 3,300-foot level of the Argonaut mine.
Section through the Moore mine on a line parallel to and 60 feet south of the 640-foot west crosscut.
Pocket veins at the Mammoth mine.
Plan of part of the 1,600-foot level, Melones mine, showing the divergence in strike between the Bull vein and the country rocks.
Partial section through the Melones mine along the line of the lower winze on the 1,100-flat vein.
Vertical section through the 610-foot winze, Eagle Shawmut mine.
Longitudinal section through the Eagle Shawmut mine, showing the distribution of the ore by kinds.
Section through the Clio shaft.