Stephanite
Here we have one of the minor ores of silver, though it also contains plentiful antimony both chemically bound together with sulphur. It has been known for a long time and is mentioned under the name Schwarzerz in the first mining/geology textbook ever written, Georgius Agriola’s De Re Metallica. Its current name was bestowed in 1845 in honour of a long forgotten Hapsburg archduke who was a mining director and ardent mineral collector in his cabinet of wonders though French speakers call it psaturose after the Greek word for fragile. Colour is black and the lustre (surface reflection) metallic though it swiftly oxidises to a dull dark patina while the Mohs hardness is a mere 2.5.
It forms as a late stage mineral in an ore deposit, usually in hydrothermal veins with famous localities being found in Saxony, Chile, Bohemia, Potosi in Bolivia at the man eating Cerro Rico that swallowed the lives of some 3 million slaves in its ongoing history, Cornwall, the Canadian Yukon, Mexico and the famous Comstock Lode of Nevada. Most material is massive but the rare attractive crystals do exist that are highly valued additions to collections.
Here we have a 2.9 x 1.3 x 1.1 cm specimen from the Canadian Yukon at the Husky mine that produces this amazing and unique iridescent columnar material, said optical effect being produced by thin layers (known as thin film interference) in the same way as the sheen caused by petrol or oil on a puddle of water. It was collected in 1977 and apparently stashed for a couple of decades in a coffee can (us rockhounds being often somewhat eccentric characters) before entering the market. No new material like this has emerged since.
Loz
Image credit: Rob Lavinsky/iRocks.com
https://www.mindat.org/min-3764.html
http://www.minerals.net/mineral/stephanite.aspx
http://bit.ly/2w6wotf
http://www.galleries.com/Stephanite
Комментариев нет:
Отправить комментарий