Black Star Diopside

Hardness: 5-6 on Mohs scale. Color: Deep black with a distinct four-rayed star (asterism) when a point light source reflects off its surface due to inclusions of magnetite or rutile. Luster: Vitreous to dull. Crystal structure: Monoclinic; prismatic crystals. Cleavage: Good in two directions at nearly 90 degrees. Specific gravity: 3.22 to 3.38.

Black Star Diopside typically forms in metamorphic rocks, such as skarns, high-grade metamorphic gneisses, and schists, as well as in some igneous rocks like kimberlites and ultramafic rocks. The formation of the asterism is due to the presence of aligned needle-like inclusions (often magnetite) within the diopside crystal during its growth. Geological age can vary widely depending on the specific rock formation.

Primarily used as a gemstone, especially in cabochon cuts to highlight its distinctive asterism. It is a more affordable alternative to black star sapphire. It is also collected by mineral enthusiasts.

Diopside is a member of the pyroxene group of minerals. The 'star' effect, or asterism, in Black Star Diopside is caused by the reflection of light off minute, oriented needle-like inclusions within the stone. When cut en cabochon, these inclusions create a dazzling four-rayed star. The phenomenon is similar to that seen in star sapphires and rubies, but diopside typically displays a four-rayed star rather than a six-rayed one.

Black Star Diopside is most commonly found in India (primarily in the state of Andhra Pradesh), though it can also be found in other localities like Russia (Yakutia), Canada, Italy, and the USA. In the field, look for dark, usually black, crystals with a vitreous to dull luster. The distinguishing feature for identifying it as 'star diopside' would be the asterism, which is best observed under direct sunlight or a single point light source after the mineral has been cut and polished into a cabochon.