Terry Mine (Terry Borate Mine; Terry pit; Terry deposit), Amargosa Valley, Inyo County, California, USAi

Regional Level Types
Terry Mine (Terry Borate Mine; Terry pit; Terry deposit)	Mine
Amargosa Valley	Valley
Inyo County	County
California	State
USA	Country

A former borate-zeolites-gypsum mine located in sec. 21, T25N, R4E, SBM, 11.0 km (6.9 miles) ESE of Ryan, at the foot of the E slope of the Greenwater Range, W edge of Amargosa Valley (2 miles S of highway 190, on a gravel road 7 miles W of Death Valley Junction). Operated by Tenneco Oil Co. (1976). Owned by American Borate Co. (1977). The deposit was mined from December, 1974 to April, 1975. MRDS database stated accuracy for this location is 1,000 meters. The deposit was discovered in 1972 from surface outcrops of colemanite. The American Borate Co. purchased Tenneco's borate holdings in 1977.

Mineralization is a Miocene borate deposit (Mineral occurrence model: Model code: 260; USGS model code: 35b.3; Deposit model name: lacustrine borates), hosted in sedimentary rocks of the Furnace Creek Formation (shale, sandstone, conglomerate, evaporite and volcanic tuff). The ore body had a depth-to-top of 18.29 meters, a width of 60.96 meters, and a length of 73.15 meters. The ore mineral is colemanite, which is typically translucent and light brown and occurs as spherical aggregates (5 to 30 cm diameter) of radiating, acicular to bladed crystals. Ulexite "cottonballs" occur stratigraphically above the ore body. Local alteration involved the zeolitization of the tuffs.

The Terry deposit is located on the northeasterly limb of the Ryan Anticline. Sedimentary features of the enclosing rocks indicate that they were deposited in a desert environment. The zeolite assemblage indicates formation in a moderately saline-alkaline lake environment. The deposit is largely colemenite with sparse hydroboracite and ulexite. Along the edges of the deposit, the colemanite is altered to calcite. Ulexite occurs in the shale surrounding the colemanite. Barker (1980) believes that the primary borate mineralization at this deposit consisted of Na-Ca borates and that the formation of colemanite occurred at depth. The deposit is essentially circular in map view and averages 6 feet thick. Colemanite outcrops at the surface, but over burden may be as much as 60 feet (15 to 290 feet average).

The Furnace Creek formation is restricted to the Black Mountains tectonic block, a NW-trending wedge between the Death Valley and Furnace Creek fault zones. Its stratigraphic thickness is estimated to exceeed 5,000 feet with major borate mineralization confined to the lower 500 feet of the section. The Furnace Creek Formation is unconformably overlain in the Terry area by basalts and volcaniclastics of the Funeral Formation. Basalts of the Furnace Creek Formation crop out within 0.5 mile of the mine.

Local geologic structures include the Grand View Fault, local N-trending fault pattern. Regional features include the SE-plunging Ryan Anticline.

Workings include surface openings comprised of a pit.

Production data are found in: Barker (1980).

Reserve-Resource data are found in: Evans, James R., G.C. Taylor, and J.S. Rapp (1976); the 1974 figure is from Barker, C.E. (1980) and in Orris, G.J. (1992).

Other Databases

Link to USGS MRDS:	10023424

Other Regions, Features and Areas containing this locality

References