Fluorspar

Fluorspar, also called fluorite, is a soft, easily workable stone that is found in many colors. It cleaves easily along four directions to form octahedrons. In the Realms, if a rough stone was pale blue, green, yellow, purple, pink or red, or was physically small, it was usually cut into faceted gems sometimes called "cabra stones". A purple-and-white banded variety was also mined in large blocks and was used for carving (see Hardstones: Archon also known as Blue John). A typical stone had a base value of 10 gp with the higher valued stones tending to be the red and pink varieties.