Brochantite
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Description
A vivid green mineral composed of tribasic copper sulfate. Brochantite was discovered by French grologist, A.J.M Brochant de Villiers. It is a secondary mineral found in oxidized zones of Copper deposits in Arizona, Chile, Mexico, and Russia. The mineral also forms as a bright green corrosion product on copper and Bronze artifacts exposed to Sulfur containing pollution. Brochantite is considered a stable patina, but may indicate pit formation for outdoor leaded bronzes due to the formation of a soluble lead sulfate.
See also Antlerite.
Synonyms and Related Terms
tribasic copper sulfate; Brochantit (Deut.); brochantite (Fr., It.); brocantita (Esp.); brochantiet (Ned.); brochantite (Port.)
Physical and Chemical Properties
- Composition = Cu4SO4(OH)6
- Mohs Hardness = 3.5 - 4.0
- Density = 3.9-4.0 g/ml
- Ref. Index = 1.771 - 1.800
- Birefringence = 0.072
- Needle-like prisms in orthorhombic crystalline system.
- Streak = pale green.
- Luster = vitreous.
- Perfect cleavage in one direction.
- Fracture = conchoidal
Resources and Citations
- Mineralogy Database: Brochantite
- Dictionary of Building Preservation, Ward Bucher, ed., John Wiley & Sons, Inc., New York City, 1996
- C.W.Chesterman, K.E.Lowe, Audubon Society Field Guide to North American Rocks and Minerals, Alfred A. Knopf, New York, 1979
- Thomas Gregory, The Condensed Chemical Dictionary, Reinhold Publishing, New York, 3rd ed., 1942
- Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
- Wikipedia: Brochantite (Accessed Sept. 2, 2005 and March 2025)