Iceland spar is rather unique among the calcites. It contains no impurities, so it’s nearly colorless and transparent to both visible and ultraviolet light. For centuries, the only source of this pure calcite was located near Reydarfjördur fjord in eastern Iceland, hence most of the world called it Iceland spar (spar means a crystal with smooth surfaces). The Icelanders just called it silfurberg, meaning silver rock.
A crystal of Iceland spar has two very interesting properties. First, it is a natural polarizing filter. Second, because of its natural polarization, Iceland spar is birefringent, meaning light rays entering the crystal become polarized, split, and take two paths to exit the crystal – creating a double image of an object seen through the crystal thus an optical prism!
Calcite cleanses the organs and strengthens the skelton and joints heals and reduces tension.