A. O. prospect, Mount General (Mt General), Hinkley, Barstow Mining District, San Bernardino County, California, USAi

Regional Level Types
A. O. prospect	Prospect
Mount General (Mt General)	Mountain
Hinkley	Unincorporated Community
Barstow Mining District	Mining District
San Bernardino County	County
California	State
USA	Country

Two miles southeast of Mount General is unnamed working BS-34, noted for vanadinite (Bezore and Shumway, 1994), and referred to as the A. O. Prospect since it was first called to SCFM [Southern California Chapter of the Friends of Mineralogy] attention by Al Ordway. This prospect has yielded colorful micros of vanadinite and descloizite. Mineralization seems to follow the marble/gneiss contacts correlated with the Waterman gneiss (Bezore and Shumway 1994). The dolomitic marble contains graphite flakes to several millimeters here and in the vicinity of many of the eastern prospects.

The A. O. Prospect was initially explored by a shallow adit, and subsequent work was with a bulldozer and backhoe. A large excavation below the adit level exposes the concentration of vanadinite/descloizite area. These minerals occur in dark porous silica in both walls of the adit, particularly on the south wall. The mineralized zone is about 4 feet (1.22 m) thick with a total depth below the original surface of 30 feet (ca. 9 m).

Cavities within the mylonitic gneiss (Bezore and Shumway, 1994) are the result of carbonate dissolution near the contact and now contain secondary silica. No cerussite or anglesite has been observed and no sulfides remain, but the silica contains iron hydroxide, indicating their former presence. All available lead has been incorporated into lead vanadate minerals.

The A. O. vanadinite varies in aspect from stubby prisms to long needles colored white, yellow and through bluish shades to black. Oddly, it is never orange or red. The rosettes of descloizite are greenish yellow. Vanadinite crystals on balls of yellow descloizite are especially attractive. Vanadinite shows well on clear druzy quartz pseudomorphs after hemimorphite. […]

The vanadate mineralization appears to have cyclic repetitions. Specimens commonly show descloizite on fresh vanadinite previously deposited on descloizite pseudomorphs after vanadinite. Copper minerals are almost absent from the main pit and no mottramite has been found. All zinc here has also been incorporated in the vanadates, and silica shells suggest the former presence of hemimorphite.

Apparently the ore removed in generating the pit where these minerals occur was shipped to a smelter since no vanadinite has been found on the dump. However, specimens of descloizite on calcite can be found on the dump. Occasional pieces contain chrysocolla with mottramite, embolite (chlorargyrite/bromargyrite), and rhombic pseudomorphs after a carbonate mineral. Specimens of mottramite on calcite also occur in a trench east of the pit. […] A single specimen from the dump yielded fresh hemimorphite and a trace of cerussite.