Bearded Geology

    Another periodic mineral post! Since the last one was realgar, an arsenic bearing mineral, I thought I'd continue the theme of toxic minerals with galena. Galena is a very dense lead sulfide mineral (the chemical formula is PbS) and is the primary ore mineral that is mined for lead. Typically associated with zinc minerals such as sphalerite (ZnS), lead has long been mined in the US since the colonial period, but today there are only  ten mines in the US that currently produce lead . Five of these are in Missouri (the Brushy Creek, Buick, Fletcher, Sweetwater, and Viburnum mines), two in Alaska (the Greens Creek and Red Dog mines), two in Idaho (the Galena and Lucky Friday mines), and one in Washington (the Pend Oreille mine). Although, there has been recent discussion in late 2018 to re-open the Bunker Hill Mine in Idaho. However, the Bunker Hill Mine is next door to the second-largest EPA Superfund site which houses the Bunker Hill smelter complex and tailing piles...

Realgar (red) with quartz and pyrite. I was thinking of periodically posting about some particular mineral, fossil, or rock (particularly when I don't have a topic to discuss), and I thought that realgar would make for a good mineral to discuss. Realgar is an arsenic sulfide mineral with the best chemical formula I've ever seen: AsS (sometimes written As 4 S 4 ). It's very soft ( hardness 1.5-2 ) with a brilliant red color and a resinous, greasy luster  and is associated with hydrothermal ore deposits. Several fantastic specimens of realgar come from Paloma, Peru (such as the one pictured). Interestingly, realgar reacts to sunlight. I don't understand exactly how this happens, but given some time in sunlight, it will alter to a yellow-orange mineral called pararealgar. So, if you collect a sample of realgar, keep it in a dark box or drawer. I didn't know about this when I got my sample (pictured), but I've been fortunate to not have enough space to displa...