Chalcocite ps. Covellite

$3,500.00

Free shipping
Seller offers an extended return window of up to 30 days
Ships from USA

T

The ArkenstoneFeatured

3,403 for sale·Member since 2026

This is a very rare and historic style of replacement pseudomorph from the Leonard Mine in Butte, Montana. It's a great miniature with distinct gray hexagonal plates of chalcocite that have replaced covellite and then highlighted with bright green malachite. In this piece, the original covellite (a copper sulfide with the formula CuS) has been replaced by chalcocite (also a copper sulfide Cu2S, but with twice as much copper), suggesting the replacement process involves the addition of copper/removal of sulfur during the later history of this piece! This is a well-defined group of original, sharp covellite crystals that have been perfectly and almost completely replaced by chalcocite, with the largest crystal 1 inch across! The crystals are currently a dark dove-gray and if you turn the piece over there is a vestige of shiny, metallic brass colored covellite in a few places on one end. The malachite provides contrast and increases the definition of the crystals! Unlike most of these we have seen, it is a sharp cluster and in good condition. It likely dates from the 1950s-1960s. Comes with a custom lucite display base. Awarded Tucson Gem and Mineral Show's best in show Paul Desautels Trophy case (2009). Illustrated in Collecting Pseudomorphs: The Changelings of Mineralogy (Mineralogical Record, Jan 2025) on page 94. Also illustrated in ExtraLapis #43: Pseudomorphs. Laszlo Kupi photo.