AUGEN GNEISS - An unusual metamorphic rock
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Locality unknown
Lenticular-shaped aggregates of feldspar crystals in gneiss. In cross section the aggregates have the shape of an eye and are called augen (derived from the German word for ‘eyes’).
Gneiss is a foliated metamorphic rock that was formed under extremely high pressures and temperatures. The banding is a result of mineral segregation into separate light and dark-coloured layers; light-coloured layers are usually composed of feldspar and quartz and dark layers are usually of hornblende and biotite.
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Size: approx. 14 x 9 x 4 centimetres
Weight: 775 grams
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