Rheniite

Rheniite is a rare mineral composed of rhenium disulfide with the chemical formula ReS2. It is one of the few naturally occurring rhenium-bearing minerals, with rhenium being a very scarce element. Rheniite typically forms in very low concentrations within hydrothermal deposits, often associated with other sulfide minerals. Its crystal structure is layered, similar to molybdenite, with rhenium atoms bonded to sulfur atoms. The color of rheniite is usually dark gray to black, and it possesses a metallic luster. It is a relatively soft mineral, with a Mohs hardness typically around 2 to 2.5. Due to its rarity and the dispersed nature of rhenium in the Earth's crust, rheniite is not a commercially viable source of rhenium. The primary sources of rhenium are byproducts of copper and molybdenum mining. Despite its rarity, rheniite is of scientific interest for geologists and mineralogists studying the geochemistry of rhenium and the formation of ore deposits. Occurrences of rheniite have been reported in a few locations worldwide, including some in the former Soviet Union and China. Its identification often requires specialized analytical techniques due to its scarcity and the presence of other similar-looking sulfides.