Characteristics of Calcite:

Chemical Name: Calcium carbonate

Formula: CaCO3

Colors: Colorless, white, various

Structure: Trigonal

Hardness: 3

Specific Gravity: 2.7

Refractive Index: 1.48-1.66

Lustre: Vitreous

Streak: White

Locations: Iceland, USA, Germany, Czech Republic, Mexico

What is Calcite? 

Although calcite forms spectacular crystals of varied shapes and in virtually all colors, most calcite occurs in the form of limestone, marble, or travertine, all of which are used as ornamental and carving stones. Travertine is a dense, banded rock formed by the evaporation of river and spring waters, depositing colored layers of calcite. Sliced travertine and marble were used extensively as a facing stone for buildings in ancient Greece and Rome, and many ancient Egyptian “alabaster” carvings are actually calcite.

The Viking Sunstone

Seafaring Vikings relied on the sun for navigation, but cloudy days posed a problem. Norse sagas talk of a “sunstone” that could help find its position on any day, grey or bright. Some scientists think this may have been calcite: a calcite crystal polarizes light into two beams, which can be lined up to find the location of the sun. Modern calcite detectors achieve this within 1 percent accuracy.