Calcite is a very common mineral, so it is hard to say that a particular person was the first to discover it. The popular colorless variety of calcite, called "Iceland Spar," was first formally described in the 1600s by a mining company working in the Helgustadir Mine in Eskifjord, Iceland.
Calcite occurs naturally in a wide variety of shapes and colors. Many varieties are considered beautiful and are sold regularly in markets across the world as jewels. A major portion of the Earth's rocks, including igneous rocks, consist of calcite, and it accounts for about 4 percent of the weight of the Earth's crust.