Magnificent birefringent calcite crystal from Berufjordur in Iceland.
Icelandic spar is a transparent variety of calcite. Birefringence is the physical property of a material in which light propagates anisotropically. A spectacular effect of birefringence is the double refraction by which a light ray penetrating the crystal is split in two. This is the case here.
Old handwritten labels attached to the specimen.
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