Optical Calcite is also known as Iceland Spar, and was originally discovered in Iceland, hence its name. It is a transparent form of Calcite, which often displays beautiful rainbows that flash in the light. It also displays the rare property of double refraction, so when placed over text it will show double the image, slightly offset. This beautiful crystal is most often seen in a colourless form, but it also forms in pink, peach and green tinged crystals, often named Watermelon Calcite for their colours. Optical Calcite can also be found in Mexico and New Mexico, USA.

Optical Calcite is believed to help individuals see the hidden or double meanings and can help to reduce tension migraines. It also acts as a powerful energy amplifier and cleanser, clearing negativity and speeding up development and growth. This crystal has strong spiritual energy and can aid and accelerate the development of higher awareness and psychic abilities. It can calm the mind, stimulate insight and memory, and aid study through retaining useful information. Optical Calcite is also helpful in combating laziness and soothing emotional stress.