Calcite is a mineral made of calcium carbonate. It is one of the most common minerals on Earth and comes in a wide variety of shapes and colors. Calcite and aragonite are polymorphous to each other; they contain the same chemical composition but differ in crystal structure.
Calcite is usually found in sedimentary, metamorphic and igneous rocks. It is the main component of limestone, marble and the Earth's crust and is one of the most widely used minerals. The properties of calcite make it suitable for agricultural soil treatment, construction material and pharmaceutical applications. Crushed limestone and marble are also used to neutralize acids in areas where streams have large quantities of acid mine drainage.
According to the University of Minnesota, calcite occurs in both crystalline and massive forms. Crystals of calcite are usually transparent to translucent, whereas masses of calcite tend to be light colored. Both these forms of calcite can create a wide range of colors when exposed to small amounts of impurities, which gives them a unique appearance depending on their location in the world. In powdered form, calcite often has an extremely white color that is used as a white pigment or "whiting," according to Geology.com.