This rare Iceland Spar crystal from of course Iceland has amazing formations with rainbows when holding the crystal up to sunlight.
Approximate Measurements - 6.2cm x 5cm x 2.5cm, 128g
It differs from regular Optical Calcite sold on the market. Although both are made of Calcium Carbonate, Iceland Spar is easily identified by its clarity and birefringence (the crystal's refractive index changes for light of different polarisations) - As light passes through this crystal, the double refraction results in seeing a doubled version of an object. Iceland spar will also tend to have numerous rainbows from its birefringence.
