Home > Type Locality Minerals II – November 7 > MS1268 Eglestonite with Terlinguaite

Eglestonite with Terlinguaite


Moses (1903) first described both eglestonite and terlinguaite, two oxychlorides of mercury. Terlinguaite starts off bright yellow, but alters to green upon exposure to light; its name honors the mining district. The name eglestonite honors professor Thomas Egleston (1832-1900) of Columbia University, New York City. Recent study indicates that eglestonite also contains hydrogen, which is difficult to measure by chemical analysis as its formula only requires 0.67% H2O (Mereiter et al. 1992).

The matrix here consists of pink claystone characteristic of the Terlingua area. On a fracture surface, among scattered calcite cleavages, there are two patches of eglestonite to 8 mm across. The eglestonite has a rich yellow-orange color, and shows a complex isometric morphology. Terlinguaite is also present as a fine yellow-green powder. This specimen was part of the Bob Kaar (1930-2003) collection, a former professor of earth sciences at the City College of San Francisco. A handwritten note states "mined in 1996".

Price: $250

Item code: MS1268

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