Because calcite is relatively soft and fragile, it is not usually an important gem mineral. This calcite gem from Balmat, New York, is a spectacular display piece and a testament to the gem cutter's art, in this case that of Art Grant. At 1,800 carats, it is also probably the largest and finest faceted calcite in the world.
Calcite is not commonly an important gem mineral because it is relatively fragile and soft (3 on the Moh's scale of hardness). It is typically colorless or white, however due to impurities it can occur in shades of red, yellow, green, blue, violet, brown, and black. This lively reddish-orange calcite from a recent find in Tanzania is rare and a wonderful addition to the National Gem Collection.