Microphotograph of a calcite geode found in a glendonite structure
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Microphotograph of a calcite geode found in a glendonite structure

by Sophie Graul, Tallinn University of Technology, Tallinn, Estonia and France

Microphotograph of a calcite geode found in a glendonite structure in Ordovician black shales. Micro mineralisations include hematite (black spherical crystals), goethite (red spherical crystals), sphalerite (silver automorphous crystals). The blue shape of the lower-right angle might be malachite.