Siderite on Pyrite & Quartz (Kay Robertson Coll.)

Item Description

This famous Bolivian tungsten-bismuth mine is noted for world-class ferberite specimens. It has also produced outstanding siderite specimens, such as this very fine two-sided combination rib. Sharp, blocky, lustrous, translucent (hard to see), mahogany-brown rhombs are nicely accented with stepped-growth faces. The siderites are dramatically clustered on the front and are dominated by the well-placed, 2.2 cm on the diagonal, rhomb. The impressive large isolated rhomb on the back is 2.5 cm om the diagonal. The sculptural matrix is covered with tiny pyrite octahedrons and quartz points. A classic, very aesthetic and exceptional older combination from the Tazna Mine from the Kay Robertson Collection # 12221 and acquired in Denver in 1990. Kay is a prominent California collector, who specialized in European classics (see the article in the March-April, 2007 Mineralogical Record). Tres Cruces is a district near La Paz and the piece was probably purchased there (thanks to a Bolivia specialist). Tazna is further south.