Antlerite is a sulfate class mineral and is a secondary mineral found in copper ore deposits with varying and attractive shades of green. Antlerite comes from the oxidation of copper ore minerals in combination with other oxidation zone minerals. The best field indicators of Antlerite are its color, glassy luster, crystal habit, cleavage, non-reaction to hydrochloric acid and its non-magnetic and non-fluorescent properties. The orthorhombic crystal system of Antlerite includes thick fibrous crystal clusters and small tabular crystals that are transparent to translucent. For a translucent mineral, Antlerite has an above average specific gravity of approximately 3.9. Antlerite crystals may also be vertically striated. The cleavage of Antlerite in one direction is perfect and in another direction is poor.
Antlerite was named by William F. Hillebrand in 1889, after the locality from which it was found - Antler mine, Mojave County, Arizona, USA.
Antlerite has a widespread occurrence. The geological setting best conducive to formation of Antlerite is in arid regions of poor carbonate-copper deposits under highly acidic conditions. Most notable occurrences include Chuquicamata, Chile, and the Antler mine in Arizona (from where it takes its name). Other occurrences are Mexico, and the USA locations of Nevada, New Mexico, California and Utah.
The Antlerite crystal is beautiful and is found in some gems, however, its brittle composition and a hardness of only 3.5 makes it less than a favorable choice for gemstone quality. Antlerite is one among many of the blue and green minerals that can attribute its color to copper, including turquoise, a phosphate gem mineral.
Once considered a rare mineral, Antlerite is the main ore of the Chuquicamata copper mines in Chile, and is confirmed to be present in many other copper mines worldwide.
The close mineral association of Antlerite is With Atacamite, Azurite, Brochantite, Chalcanthite, Cuprite, Gypsum, Krohnkite, Limonite, Linarite, Malachite and Natrochalcite. Antlerite is so visibly similar to Brochantite that it takes more than ordinary means to distinguish the two. Malachite is another of the green copper minerals that forms in the oxidation zones and is very similar to Antlerite. When exposed to warm hydrochloric acid, acicular malachite will effervesce, while Antlerite will not.
Green - Bluish green, Emerald green, Light green, Black-green, Streaks of Pale green