Brochantite

Copper sulfate mineral
(repeating unit)Cu4SO4(OH)6IMA symbolBct[1]Strunz classification7.BB.25Crystal systemMonoclinicCrystal classPrismatic (2/m)
(same H-M symbol)Space groupP21/aIdentificationColorGreen, emerald green, or blackCrystal habitPrismatic crystals; acicular needle-like crystals; druseCleavagePerfect [100]FractureConchoidalTenacitybrittleMohs scale hardness3.5–4.0LusterVitreous to pearlyStreakPale greenDiaphaneityTransparent to translucentSpecific gravity3.97Optical propertiesBiaxial (−)Refractive indexnα = 1.728 nβ = 1.771 nγ = 1.800Birefringenceδ = 0.072PleochroismWeak2V anglemeasured: 72°References[2][3][4]

Brochantite is a sulfate mineral, one of a number of cupric sulfates. Its chemical formula is Cu4SO4(OH)6.[2][3][4] Formed in arid climates or in rapidly oxidizing copper sulfide deposits, it was named by Armand Lévy for his fellow Frenchman, geologist and mineralogist A. J. M. Brochant de Villiers.[4]

Crystals of brochantite can range from emerald green to black-green to blue-green, and can be acicular or prismatic. Brochantite is often associated with minerals such as malachite, azurite, and chrysocolla, and may form pseudomorphs with these minerals.

The mineral is found in a number of locations around the world, notably the southwestern United States (especially Arizona), Serifos in Greece and Chile.

Brochantite is a common corrosion product on bronze sculptures located in urban areas, where atmospheric sulfur dioxide (a common pollutant) is present. Brochantitie forms mainly in exposed areas where weathering prevents accumulation copper ions and enhancement in the acidity of water films.[5] In sheltered areas, the main corrosion product is antlerite.

Gallery

  • These long slender crystals, from Bisbee, Arizona, have the highly desirable emerald green color and good luster that is sought after in brochantite by collectors. Detail of thumbnail specimen, size 2.3 × 2 × .8 cm.
    These long slender crystals, from Bisbee, Arizona, have the highly desirable emerald green color and good luster that is sought after in brochantite by collectors. Detail of thumbnail specimen, size 2.3 × 2 × .8 cm.
  • Brochantite on chrysocolla. Locality: Rokana Mine, Kitwe, Copperbelt Province, Zambia. Detail of larger specimen, field of view about 3 × 5 cm.
    Brochantite on chrysocolla. Locality: Rokana Mine, Kitwe, Copperbelt Province, Zambia. Detail of larger specimen, field of view about 3 × 5 cm.
  • Brochantite on linarite. Locality: Mujuram, Morocco. Size 8 × 8 cm.
    Brochantite on linarite. Locality: Mujuram, Morocco. Size 8 × 8 cm.

References

  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b Webmineral
  3. ^ a b Mineral Handbook
  4. ^ a b c Mindat
  5. ^ Leygraf C, Graedel TE. Atmospheric corrosion. New York: Wiley-Interscience; 2000. ISBN 0471372196

External links

Wikimedia Commons has media related to Brochantite.
Wikisource has the text of the 1911 Encyclopædia Britannica article "Brochantite".