calcite

This mineral is characterized by its distinct rhombohedral cleavage and double refraction, which creates a visual doubling of images when viewed through a clear crystal. It is the most common carbonate mineral found in nature, often forming stalactites and stalagmites in cave environments. In industrial applications, it is valued for its chemical stability and white color, making it a preferred filler in construction materials and coatings. Because it is a primary constituent of limestone, it is central to both geological study and the production of cement.