Cyanotrichite is a hydrous copper aluminium sulfate mineral with formula Cu₄Al₂[(OH)₁₂|SO₄]·2H₂O, also known as lettsomite. Cyanotrichite forms velvety radial acicular crystal aggregates of extremely fine fibers.
 
It is an oxidation product of primary copper mineralization in a weathering environment with abundant aluminium and sulfate. Associated minerals include brochantite, spangolite, chalcophyllite, olivenite, tyrolite, parnauite, azurite and malachite.

Cyanotrichite
Formula: Cu4Al2(SO4)(OH)12 · 2H2O
Colour: Sky-blue, azure-blue
Lustre: Silky
Hardness: 1 - 3
Specific Gravity: 2.76
Crystal System: Orthorhombic
From (Qinglong Mine, China)
 
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