Diopside is a mineral that is relatively unknown in the jewellery world. It is appears as a crystal and as a massive structure composed of calcium magnesium silicate.
The massive structure, usually black, is often impregnated with parallel needles of other microcrystalline minerals, which give the illusion of a ray of light moving across the surface of the stone from within. This property is known as “chatoyancy”, for the cat-eye effect it creates. If they formed at 90 degrees to each other, the stone can be cut “en cabochon” and a four sided star will appear under sunlight. This particular type of chatoyancy is called “asterism”, after the star it creates. In diffused fluorescent light, a misty bright cloud will appear to float under the surface. Star Diopside has often been mistaken for Star Sapphire by the uninitiated, but the Sapphire always has six points.
By contrast, the crystalline form is typically green in colour, and usually cut into a very bright and sparkly gem.
Diopside is found in Burma, India, South Africa, Finland, Italy, and Austria. It is fairly easily cut due to a relative softness of the calcium. However, it will fracture on impact and so it is better as a pendant or set of earrings than as a ring stone. The better stones are in the medium price range and are competitive with Tourmaline, Spinel and Topaz. Fine quality diopsides can, and do, command a premium.
Diopside is an excellent choice as a natural stone for the collector or the person who wants something unique.