Home > American Minerals II – April 7 > MS1550 Gerstleyite


Gerstleyite is a hydrous sodium antimony sulfide (Frondel & Morgan, 1956). Nakai & Appleman (1981) solved the crystal structure, placing gerstleyite among the sulfosalt minerals (Moëlo et al., 2008). The mineral name honors James M. Gerstley (1907-2007), president of the Pacific Coast Borax Company. Pacific Coast Borax sponsored an old-time radio show and later a television program, Death Valley Days, in order to promote its 20 Mule Team Borax product.

Gerstleyite here forms three red masses, 11 by 8 mm, 5 by 5 mm, and 3 by 4 mm, in clay. The gerstleyite masses show minute cleavage surfaces, indicating grain sizes up to 0.5 mm in this example. The matrix consists of greenish-gray clay characteristic of this locality, with minor bladed probertite and powdery white tincalconite. The matrix will not survive washing in water; it would disintegrate. Gerstleyite is known only from the Kramer deposit. This piece was part of the collection of Richard C. Erd (1924-2008), mineralogist at the United States Geological Survey at Menlo Park. Erd's label accompanies the specimen.

Price: $350

Item code: MS1550

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