cookeite

Cookeite is a mineral species of the silicate group and the phyllosilicate subgroup, part of the chlorite family, with the formula LiAl4(Si3Al)O10(OH)8. This soft, low-density mineral of variable color has a crystalline structure made up of alternating layers LiAl2(OH)6 and Al2O4(OH)2Si8O12 having several polytypes. Cookeite is often found as a product of hydrothermal alteration of silicates in pegmatites. It forms at relatively low temperatures (below 200°C) and variable pressures.

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Nickel-Strunz 9th edition (updated 2009): 9.EC.55
Nickel-Strunz '10th ed', review of (9th ed/ 2009 update): 9.EC.55
Commons category: Cookeite
Commons gallery: Cookeite
IMA Mineral Symbol: Ckt
chemical formula: (Al,Li)₃Al₂(Si,Al)₄O₁₀(OH)₈
Strunz 8th edition (series ID, updated): VIII/E.09a

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Article

19 sections

Contents

History
Inventor and etymology
Topotype
Physico-chemical properties
Determination criteria
Chemical composition
Crystallochemistry
Crystallography
Overview
Cookeite r
Other cookeites
Mineral deposits
Geology and associated minerals
Productive deposits of remarkable specimens
Mineral growth
Notes
References
Appendix
Bibliography

{{Infobox mineral|name=Cookeite|image=Cookeite.jpg|caption=Cookeite on quartz, Paris, Maine, topotype deposit|category= Phyllosilicate minerals|group=Chlorite group|formula=|strunz=09.EC.55|system=monoclinic|dana=71.04.01.02|class=prismatic;C2 or Cc|color=white, green, brown, golden, pink|twinning=around [310]|cleavage=perfect over {001}|fracture=flexible|tenacity=2,5|luster=pearly; silky|refractive=α = 1,572–1,576, β = 1,579–1,584, γ = 1,589–1,6|birefringence=biaxial (+), 0,0170–0,02402V = 35 to 60°|pleochroism=x = y: pale green to pink, z: colorless to pale yellow|fluorescence=cream yellow (SW)|density=from 2.58 to 2.69}}