Cyanotrichite Crystals

Cyanotrichite is a wonderfully colored mineral. Its bright azure to sky blue color is very impressive. Cyanotrichite typically forms acicular or hair like crystals aggregated into radial clusters, tufts and sprays. The color is very impressive for such tiny crystals. It is an aptly named mineral since cyano and trich are derived from the Greek for blue and hair, respectively. It is formed from the oxidation of copper ore minerals along with other oxidation zone minerals

 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 Crystals. From Qinglong Mine, China.
Photo: © Matteo Chinellato

Cyanotrichite Properties

  • Chemical Formula: Cu4Al2(SO4)(OH)12 · 2H2O
  • Colour: Sky-blue, azure-blue
  • Lustre: Silky
  • Hardness: 1 - 3
  • Specific Gravity: 2.76
  • Crystal System: Orthorhombic
  • Streak is blue.
  • Crystal Habit:
    • Velvety, wool- or cotton-like aggregates and coatings comprised of minute acicular crystals
    • Radial-fibrous or tufted
  • Associated Minerals are brochantite, smithsonite, malachite and azurite.
  • Notable Occurrences include Laurium, Greece; Leadhills, Scotland; Russia; South Africa; Arizona, Nevada and Utah, USA and France.
  • Best Field Indicators are crystal habit, associations and color.


Cyanotrichite crystals from Chile
Photo: Henk Smeets/Tomeik Minerals.
Cyanotrichite from Christiana Mine, Attikí (Attica) Prefecture Greece
Photo: Horst-knoll

Fuzzy balls of cyanotrichite on malachite from Grand Canyon, Coconino County, Arizona

Cyanotrichite crystals

Cyanotrichite from Qinglong Mine, Dachang Sb ore field, Qinglong County, Qianxinan, Guizhou, China

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