Optical calcite, also known as "Icelandic Spar” is a form of calcite that is famous for its optical properties.
This beautiful, rainbow filled crystal can transmute and cleanse energy, aid detox and accelerate personal and spiritual growth; it’s reported that Optical Calcite can also facilitate psychic awareness and astral travel. 
This piece weighs 169g and measures approximately 1.8 x 1.8 x 1 inch