Corrensite from Nasławice (Lower Silesia, Poland): Some Problems of Mineral Identification and Origin

Elżbieta Dubińska1, Paweł Bylina2 and Boris A. Sakharov3
1 Institute of Geochemistry, Mineralogy and Petrography, Geological Faculty, Warsaw University al. Żwirki i Wigury 93, 02-089 Warsaw, Poland
2 Institute of Geological Sciences, Polish Academy of Sciences al. Żwirki i Wigury 93, 02-089 Warsaw, Poland
3 Institute of Geology, Russian Academy of Sciences Pyzhevsky per. 7, 109017 Moscow, Russia

Abstract: The corrensite from a chlorite vein-like rodingite blackwall in serpentinites has been studied. The proper identification of swelling layers in corrensite using heating at 500°C was ambiguous because of the spontaneous rehydration. Even K+-saturated samples heated to 500°C readily rehydrated after being cooled. This can be prevented if XRD patterns are recorded at 300°C without cooling the sample. A standard heating at 500°C can result in partial decomposition of brucite-like sheet as evidenced by ASN simulation.

The ASN-calculated XRD patterns of contracted corrensite proved that an inhomogeneous distribution of heavy atoms (Fe, Ni, Mn, Cr etc.) between brucite-like sheet and talc-like layers and between two adjacent corrensite units in the interstratified mineral may result in the disappearance of low angle reflections (24 Å, and 12 Å), which can lead to miscellaneous interpretation if distribution of heavy cations is not checked.

The corrensite occurred together with regular chlorite. However, it is assumed to be formed due to direct crystallization from late hydrothermal solutions as deduced from comparison of the Mg/(Mg + Fe) ratio in the corrensite, serpentinite and chlorite.

Key Words: Calculated X-ray patterns • Corrensite • Thermal contraction • X-ray powder diffraction

Clays and Clay Minerals; October 1995 v. 43; no. 5; p. 630-636; DOI: 10.1346/CCMN.1995.0430513
© 1995, The Clay Minerals Society
Clay Minerals Society (www.clays.org)