Abstract The Kramer borate deposit is located in the northwestern Mojave Desert, about 90 air miles northeast of Los Angeles and 3 miles north of the town of Boron (figure 1). The deposit derives its name from the mining district in which it lies. The Kramer deposit, presently being mined from the Boron open pit, has been a world-class source of sodium borates since mine startup in 1926 and continues to be the largest source of borates in the world. The Kramer ore body is a roughly lenticular sedimentary sequence of borax (Na 2 B 4 O 7 • 10H 2 O) and kernite (Na 2 B 4 O 7 • 4H 2 O) containing interbedded claystone. This central crystalline facies is successively enveloped by facies consisting of ulexite (Na,CaB 5 O 9 • 8H 2 O) -bearing claystone, colemanite (Ca 2 B 6 O 11 • 5H 2 O) -bearing claystone, and barren claystone. Studies indicate the Kramer borates were deposited in a small structural, nonmarine basin, associated with thermal (volcanic) spring activity during Miocene time. The Kramer deposit does not crop out. It was discovered accidentally in 1213 by Dr. John Suckow, a homesteader, who struck colemanite while drilling a water well (figure 2). Exploratory drilling and shaft sinking after World War I by Pacific Coast Borax Company, the predecessor of U.S. Borax, led to the discovery of borax and kernite in 1925. In 1926 PCB went into large-scale, underground sodium borate mining in the Baker mine, located nearly 2 miles east of Suckow's discovery well. The company soon closed all its calcium borate operations near Ryan in Death Valley in favor of the more easily processed sodium borates at Boron. U.S. Borax ships mostly bulk, refined sodium borate products and boric acid to both domestic and world markets from Boron. Principal uses for these products are in the manufacturing of glass and fiberglass, herbicides, ceramics, soaps and detergents, fluxes, fertilizers, and fire retardants.

Abstract Sulphur Bank is the most productive mineral deposit in the world that is clearly related to hot springs. The ore is late Quaternary and is localized in rocks immediately below the water table that existed prior to mining. The hydrothermal alteration and the mineralogy of the veins have been controlled largely by the water table. The upper part of an andesite flow has been above the water table and is extensively altered by sulfuric acid formed by oxidation of H2S. Characteristic alteration minerals are opal, cristobalite, and anatase where leachi ng has been intense, and kaolinite, halloysite, alunite, soluble sulfates, and perhaps jarosite and montmorillonite where acid attack has been less intense. Native sulfur without cinnabar was abundant near the surface, but, as the water table was approached, sulfur decreased, and cinnabar became abundant. The principal ore bodies were at and below the water table and consisted of cinnabar, marcasite, pyrite, dolomite, calcite, quartz, a zeolite mineral, and all the minerals of the original rocks. Metacinnabar and stibnite were locally common. The waters deep in the spring system appear to be nearly neutral, but near the water table they become slightly acid because of mixing with downward percolating waters containing H 2 SO 4 resulting from oxidation of H 2 S. Films of condensate in the areas of most intense acid leaching may have pH values of 1 or less. The present thermal waters are very highin total CO 2 , boron, ammonia, sodium, and iodine and are low in silica and potassium as compared to many thermal and mineral waters. Chemically and isotopically they are unlike most thermal waters associated with recent volcanism. The present rate of discharge of water of deep origin is calculated to be about 50 gpm. T h e average concentration of quicksilver in the ore solutions was probably 0.05-8 ppm, assuming an interval of deposition between 10,000 and 100,000 years and a rate of discharge of water of 50–1000 gpm. The most reasonable estimate is believed to be 0.1–1 ppm. Present temperatures are relatively low compared to other hot-spring systems of clearly volcanic origin . The present heat flow is on the order of 200,000 cal per sec, or about 12 times “normal” for the area; total heat flow inthe past may have been as much as 20 times as much. The heat is almost certainly volcanic in origin, but, despite association with Quaternary volcanic rocks and volcanic heat, the chemical and isotopic compositions of the water and gases now being discharged indicate that these fluids are nonvolcanic i n origin.