Diopside is a calcium magnesium silicate with a hardness of 5.5 to 6. Its crystal system is monoclinic. It most commonly forms in short prismatic crystals, which are often twinned. It can also be found in columnar, granular or massive habits. Its color is usually white to light green, but it can also appear in darker shades of green, as well as reddish brown, yellowish brown, gray or greenish black. Sometimes the crystals are cut into faceted gems, cat’s eyes or four-rayed cabochon stones. The most important localities for Diopside are in China, India and New York, USA.