Quartz

specimen number:
9892120

location:
Blackwell mine, Tiff, Washington Co., Missouri, USA

description:
Glistening colorless translucent quartz measuring to 0.4 cm in size covering the top of an agate matrix. In very good condition. Classic material for the species and area.

The Blackwell mine in Tiff, Washington County, Missouri, lies within the famous Potosi mining district, where late Cambrian dolomite formations weathered to produce thick deposits of residual red clay containing rich concentrations of minerals. Mining history in this area began with early surface collecting of barite, locally termed tiff, and expanded through open-pit commercial operations that processed the clay for oil drilling and industrial applications. Geologically, hydrothermal fluids filled cavity networks in the host rock, precipitating sparkling coatings of drusy quartz alongside agate and bladed barite crystals. Collectors valued the Blackwell site for producing fine mineral specimens, especially delicate, lustrous drusy quartz crusts that matrix-support or intergrow with reddish barite.

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