JDMISGem Reference
Carbonate (calcite group) · Calcite

Iceland Spar

Iceland Spar — Calcite

Iceland spar is water-clear optical calcite whose 0.172 birefringence doubles every image through the stone. Sold as cleavage rhombs and teaching specimens rather than cut gems; hardness 3 and perfect cleavage rule out wear. Iceland's Helgustadir mine is the historic source.

Colour
colourless to white
Transparency
Transparent
RI
1.486–1.658
SG
2.65–2.75
Mohs
3.0
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