Abstract Gems & Gemology, Spring 2013, Vol. 49, No. 1

Azurite Through the Ages: Millennia of Mining Have Not Depleted Its Sources

B. Jones, Rock & Gem, August 2012, pp. 20–24.

Azurite, a copper carbonate, is a common secondary mineral. The host is usually a volcanic rock. Most Collectors’ azurite crystals come from Chessy in France (the oldest mine, dating back to the mid-1800s), Morenci and Bisbee in Arizona, Tsumeb in Namibia, and Touissit in Morocco. The rising price of copper in the past decade led to the reopening of old copper mines and subsequent discoveries of well-crystallized azurite specimens from China, Morocco, and Mexico.

The quality of well-crystallized samples from the decade-old Milpillas mine in Mexico could be compared to these collectors’ samples. Azurite crystals such as the Electric Blue from Milpillas show dark blue color with high luster; they are usually one- or two-inch prisms or blocky crystals up to four inches long. They were gradually pseudomorphed into malachite in a high oxidizing environment. Thus malachite is more abundant than azurite. Sometimes a thin layer of azurite is deposited atop malachite as the final layer. The light to dark green malachite pseudomorphs from the Milpillas mine tend to be blocky crystals, ranging from one to ten inches in size. The Milpillas mine has also yielded emerald-green bronchantite, a hydrous copper sulfate, in one- or two-inch needle-like crystals on a rhyolite matrix. Free copper ions of bronchantite absorb all wavelengths except green, causing a bright green color.

Abstracted by Kyaw Soe Moe