Diopside vs. Dioptase — What's the Difference?

Diopside belongs to the pyroxene group of minerals and typically forms in metamorphic environments, particularly in marbles and gneisses. Whereas, dioptase is a rare copper silicate mineral that crystallizes in the trigonal system and is often associated with oxidized copper deposits. Diopside can be found in a variety of locations globally but is notably prevalent in metamorphic rocks. On the other hand, dioptase is significantly rarer and is prized by mineral collectors for its vibrant emerald-green color, which is due to its copper content.

The physical properties of diopside include a Mohs hardness of 5.5 to 6.5 and a white to light green streak. In contrast, dioptase has a similar hardness but is distinguished by its bright green streak and more vitreous luster. Diopside is often used in jewelry and as an ornamental stone, while dioptase, due to its rarity and striking color, is mainly collected as a specimen mineral.

Diopside's typical crystal habit includes columnar to tabular forms, and it may exhibit a green to colorless appearance. Conversely, dioptase crystals are typically small but well-formed hexagonal prisms, with a deep blue-green hue that makes them highly sought after in gem and mineral collections.