This Mineral Specimen comes with a Fact Filled Information Card .... Calcite (CaCo3) also known as Iceland Spar is a very common mineral, composed mainly of calcium carbonate. Optical calcite has a rhombohedral crystal structure and is colorless and transparent. It is used in making optical instruments, particularly polarizing microscopes.       Optical calcite possesses the unique ability to split one ray of light into two rays of light, otherwise known as double refraction. an object viewed through this crystal will be seen doubled. If the clear calcite crystal is rotated, one image remains stationary while the other image revolves. The stationary image is the ordinary ray. the rotating image is the extraordinary ray, which is polarized at 90 degrees to the ordinary ray. Picture is representative of the specimen you will receive.  Each rock is unique and will vary in shape, size, thickness and appearance.  No two rocks are exactly alike.Quantity: 1 Optical Calcite Rock.   Origin: North America  Ages 8 and up