Green Mountain Mine (Calaveras Crystal mine), Chili Gulch (Chile Gulch ?), Mokelumne Hill, Mokelumne Hill Mining District, East Belt, Calaveras County, California, USAi

Regional Level Types
Green Mountain Mine (Calaveras Crystal mine)	Mine
Chili Gulch (Chile Gulch ?)	Gulch
Mokelumne Hill	Hill
Mokelumne Hill Mining District	Mining District
East Belt	- not defined -
Calaveras County	County
California	State
USA	Country

A classic locality for "Mokelumne Hill Rock Crystal"

A former placer/drift Au and rock crystal mine located in the S½NE¼ and N½SE¼ sec. 24, T5N, R11E, MDM, in Chili Gulch, about 2 miles S of Mokelumne Hill, and N of, and adjacent to, the Rough Diamond drift mine.

NOTE: This locality is not listed in the USGS MRDS database under either name. Coordinates provided are for the center of the boundary between the NE¼ and the SE¼ of section 24.

The Green Mountain mine was first active around 1874 when it was originally worked as a drift mine. Large Quartz crystals and opalized Wood were reportedly found in the cemented, Gold rich gravels prior to 1896, and 12 tons of crystal valued at $18,000 was mined and shipped in 1897-98. In 1908, the mine failed to yield Gold, but $10,000 worth of gem quality Quartz crystals were recovered. The Green Mountain mine was idle between 1910 and World War I, but by the end of that war had produced 22 tons of crystals, the largest of which was 6 feet long and weighed 2800 pounds. The next recorded activity was in 1925, when a 700-foot drift was driven on the Green Mountain extension; a small amount of Gold being produced in 1926. Little work was done with the property until exploration for Quartz crystals resumed in May of 1943, when the property was operated as the Calaveras Crystal mine. By June of that year the exploratory drift was 675 feet long, and 300 pounds of Quartz crystals had yielded 90 pounds of salable material. Quartz production continued through 1944, but no production has been reported since that year.

The Green Mountain mine is located on the Tunnel Ridge channel, which flowed south-west at the time its gravel was deposited. This channel is truncated 900 feet north of the mines by a younger channel that contains a thin section of basal gravel capped successively by Rhyolitic ash and Andesitic cobbles and ash. The Tunnel Ridge channel cuts Greenstone and Slate of the Calaveras group and is filled entirely by gravel, which here is 1200 feet wide and 285 feet thick. The gravel is composed of well-rounded Quartzite, vein Quartz, and Quartz Shist, with lesser amounts of altered Slate, Greenstone, Mica Shist and Serpentine.

The width of the crystal bearing gravel at the Green Mountain mine is 70 feet. Quartz crystals have been found as much as 20 feet above bedrock, although they are most abundant in the lower six feet of gravel. The distribution of the crystals, together with their almost complete lack of wear, suggests that their source is a nearby hydrothermal vein that was cut and eroded by Tertiary streams. There is no evidence to indicate whether any part of this vein still exists, or whether it might still contain Quartz crystals.

Other Regions, Features and Areas containing this locality

References