Tennantite

Description

Tennantite has a hardness of 3 – 4½ and a specific gravity of 4.65. Originally described as a “gray sulphuret of copper in dodecahedral crystals” in 1817 by James Sowerby, and then renamed in 1819 by William Phillips in honor of Smithson Tennant, an English chemist who established the beneficial nature of using limestone to reduce soil acidity, according to Mindat.

WebMineral analyzed a specimen and found it contained roughly 48% Copper, 28% Sulfur, 20% Arsenic, and 4% Iron, so this would make for a brilliant sample of any of the four elements for element collectors, but this would look possibly even more at home with a Colorado mineral collector!

In addition to the four elements listed above, Wikipedia included that Zinc, and Silver can also sometimes substitute up to about 15% for the Copper. Additionally from Wikipedia, Tetrahedrite is often difficult to distinguish from Tennantite as the two have very similar properties, but it contains a Antimony. They’re both found in hydrothermal veins and in contact metamorphic deposits in association with other Cu–Pb–Zn–Ag sulfides and sulfosalts, pyrite, calcite, dolomite, siderite, barite, fluorite and quartz in a couple thousand localities worldwide and around 200 in Colorado.

Interestingly, and also from Wikipedia, “the arsenic component of tennantite causes the metal smelted from the ore to be harder than that of pure copper, because it is a copper-arsenic alloy. In the later 20th century, it was found that arsenical coppers had been more widely used in antiquity than had been previously realised, and it has been proposed that discoveries made by smelting ores like tennantite were significant steps in the progress towards the Bronze Age.”

Arsenic isn’t very valuable or something you should mess with unless you know better, but the Copper is definitely something worth keeping this mineral in mind and your eyes on the ground to try to find, and you may just be able to make a fortune if you open you new Copper mine!