Grey crystal aggregates of the rare mineral corrensite on a quartz matrix. From Luzerne County, Pennsylvania, United States of America. Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY 4.0
Corrensite
Corrensite is an IMA-recognized mineral species in the silicate class, with the chemical formula (Ca,Na,K)₁₋ₓ(Mg,Fe,Al)₉(Si,Al)₈O₂₀(OH)₁₀·nH₂O.
It is a member of the Corrensite, Clay structural group.
Key properties: Dull, earthy luster; optically biaxial.
IMA symbol Crr, grandfathered status — known before the IMA’s founding, named in 1954.
From diverse sedimentary environments, which produced clastic, carbonate, volcanoclastic, or evaporite rocks. Also a hydrothermal alteration product, may be formed under retrograde diagenetic conditions; in soils.
It is found associated with Illite, chlorite, laumontite, gypsum, anhydrite, quartz, dolomite.
The name refers to Professor Carl Wilhelm Correns (1893–1980), Director of the Sedimentary Petrography Institute, GÄottingen University, GÄottingen, Germany.