Questions and phone orders: 10 AM - 10 PM Pacific (760) 920-6465
2 left

aragonite - "cave calcite" - El Potosi Mine, Santa Eulalia Mining District, Chihuahua - hand/display specimen

$ 15.00

aragonite CaCo3

Aragonite is a pseudomorph of calcite, with the same chemical formula, calcium carbonate, but a different crystal structure. When carbonated groundwater contains calcium, it most commonly precipitates calcite when cold and aragonite, when hot.

Sometimes called "cave calcite," this aragonite comes from the Potosi Mine in the Santa Eulalia Mining District, Chihuahua, Mexico. The silver, lead, zinc and copper ores in this mine are associated with thick-bedded limestones overlain by a series of rhyolite flows and tuffs. In 1912, miners broke into a cavern lined with cave calcite forms similar to these specimens. In subsequent years, numerous cavities have been discovered, with at least some specimens extracted before the cavern was destroyed by mining.

As described in 1925 by mining engineer Carl Millikan, "one cave, the 'Gypsum' cave, when opened, presented a fairyland-like scene. Pure dazzling white, filled with crystals of all shapes and sizes, it was a bonanza for specimens of everything - but ore."

Two of these fluoresce under shortwave ultraviolet. The photo under shortwave follows the normal lighting photo of the same specimen. The shapes don't match well, as the fluorescence was photographed in a different orientation. With the others, the fluorescence is weak or spotty.

The pencil is 5.5" long, for scale.


Select a specimen: When more than one specimen is shown, you can select a particular specimen by telling us what is in the photo with it, a black mechanical pencil, or pencil plus some number of coins, or you can let us make the selection.

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. See comment at Note! Use back button to return to this page.