Liroconite Explained

Liroconite

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Category:

Arsenate minerals

Formula:

Cu₂Al[(OH)₄|AsO₄]·4(H₂O)| IMAsymbol = Lro^[1] | molweight = | strunz = 8.DF.20| dana = | system = Monoclinic| class = Prismatic (2/m)
(same H-M symbol)| symmetry = I2/a| unit cell = a = 12.66, b = 7.57
c = 9.89 [Å]; β = 91.25°; Z = 4| color = Bright blue to green| colour = | habit = Typically as striated flattened octahedral or lenticular crystals, also massive to granular| twinning = | cleavage = Indistinct on and | fracture = Irregular/uneven, conchoidal| tenacity = | mohs = 2–| luster = Vitreous to resinous| streak = Light blue| diaphaneity = Transparent, translucent| gravity = 2.9–3| density = | polish = | opticalprop = Biaxial (−)| refractive = n_α = 1.612 n_β = 1.652 n_γ = 1.675| birefringence = δ = 0.063| pleochroism = | 2V = Measured: 67°| dispersion = | extinction = | length fast/slow =| fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = ^{[2] [3] [4]} }}Liroconite is a complex mineral: Hydrated copper aluminium arsenate hydroxide, with the formula Cu₂Al[(OH)₄|[[Arsenic|As]]O₄]·4(H₂O). It is a vitreous monoclinic mineral, colored bright blue to green, often associated with malachite, azurite, olivenite, and clinoclase. It is quite soft, with a Mohs hardness of 2–2.5, and has a specific gravity of 2.9–3.0.It was first identified in 1825 in the tin and copper mines of Devon and Cornwall, England. Although it remains quite rare it has subsequently been identified in a variety of locations including France, Germany, Australia, New Jersey and California.

The type locality for liroconite is Wheal Gorland in St Day, Cornwall in the United Kingdom. The largest crystal specimen on public display is in the Royal Cornwall Museum in Truro.^[5]

It occurs as a secondary mineral in copper deposits in association with olivenite, chalcophyllite, clinoclase, cornwallite, strashimirite, malachite, cuprite and limonite.

Structure

Liroconite crystallizes in the monoclinic crystal system.^[6] The crystal structure consists of a framework of AsO₄ tetrahedra, Jahn-Teller-distorted [CuO₂(OH)₂(H₂O)₂] octahedra and [AlO₂(OH)₄] octahedra.^[7]

See also

• Kernowite – an isostructural mineral with iron in place of aluminium

References

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Notes and References

1. Warr. L.N.. 2021. IMA–CNMNC approved mineral symbols. Mineralogical Magazine. 85. 3. 291–320. 10.1180/mgm.2021.43. 2021MinM...85..291W. 235729616. free.
2. http://www.mindat.org/min-2413.html Mindat.org: Liroconite mineral information and data
3. http://www.webmineral.com/data/Liroconite.shtml Webmineral data
4. http://rruff.geo.arizona.edu/doclib/hom/liroconite.pdf Handbook of Mineralogy
5. Web site: Liroconite . Aubrey-Jones . David . 2008 .
6. Kolesova . R.V. . Fesenko . E.G. . Dec 1968 . Determination of the crystal structure of Liroconite Cu₂Al[AsO₄](OH)₄ ⋅ 4 H₂O ]. Soviet Physics – Crystallography . Rostov University . 13 . 3 . 396–402.
7. Peter C. . Burns . Ray K. . Eby . Frank C. . Hawthorne . Refinement of the structure of liroconite, a heteropolyhedral framework oxysalt mineral . . 1991 . 47 . 5 . 916–919 . 10.1107/S0108270190010939 .