Dogtooth Calcite is a variety of Calcite that forms as multiple scalenohedral crystals. Dogtooth Calcite is often referred to as Dog-toothed Spar. (Spar is a general term for transparent to translucent, generally light-colored and vitreous crystalline minerals.) Dogtooth Calcite is an unusual variety of calcite and isnamed "Dogtooth" because the stone itself...
named "Dogtooth" because the stone itself looks like a large collection of dogs teeth. It has some standard colorings from clear through golden, white, grey, tan, brown and purple to name a few, but also is found some rarer shades.
Dogtooth Calcite is often found in caves as a speleothem growing out of limestone. These caves often have standing water that is seasonal or undisturbed for many years to allow these unique formations to grow. Dogtooth calcite crystals are not limited to caves, but can grow in any open space including veins, fractures, and geodes.
The sharply tooth-shaped crystals typically consist of acute scalenohedrons, triangular crystal faces that ideally form scalene triangles. (In a scalene triangle, all sides and all angles are unequal. An example is a right triangle, but scalene triangles are not always right triangles.) However, modification of these faces is common, and individual crystal faces may have many more than three edges.