chalcopyrite - larger student specimens from a skarn in Mexico's Sierra Madre - Unit of 5 student specimens

chalcopyrite CuFeS2 El Bolívar Mine Piedras Verdes District, municipality of Uruque, Chihuahua, Mexico The Bolívar Mine is an historic underground copper-zinc mine, working a skarn formed during contact metamorphism of carbonate-bearing rocks. Located in an area of northwestern Mexico's Sierra Madre that has been mined and prospected for polymetallic copper-zinc-lead-silver-and gold deposits since the Spanish colonial period, it produced around three million tons of ore between 1980 and 2000. The mine is currently owned and operated by Sierra Metals Inc. It is shown in the field photo. Chalcopyrite is the primary sulfide ore of copper. The brassy yellow color, hardness 3.5-4, and greenish gray streak distinguish it from pyrite, hardness 6-6.5, which is paler, cannot be scratched by a nail and which has a brownish black streak. As chalcopyrite weathers, it becomes a dull gray-green. If treated with a combination of sulfuric and phosphoric acids, it oxidizes to form an iridescent blue and purple surface, making it look like bornite, Cu5FeS4. It is then sold as "peacock ore," which was the common name for bornite, with its natural purplish oxidized surface. Untreated chalcopyrite should look brassy, though it may naturally develop a slight tarnish. In Germany in the 1960s, chalcopyrite was oxidized by being cooked in a solution of detergents containing perborate, such as Persil, and vinegar. We prefer that students see chalcopyrite as it comes from the mine. These specimens are natural. Both chalcopyrite and bornite are found in oxidized hydrothermal veins, but bornite occurs in an enriched zone just below the water table, while chalcopyrite is a massive sulfide of the original vein. The photo is representative of what we ship. The pencil is 5 1/2" long, for scale. Making multiple purchases? Click on the "combine shipping" button in the shopping cart. We'll send an invoice with combined shipping. A link in that invoice will bring you back to checkout, no hassle. Shipping: By Priority Mail or USPS Ground Advantage, whichever is cheaper, unless we find a better rate. Click > here < for shipping rates. Use back button to return to this page.