Known as a stone to be helpful in academic pursuits and aid creativity, Black Star Diopside is a great alternative to the usual black-gem suspects. Referred to as the ‘Black Star of India’, this slick, black beauty displays a spectacular light effect called an asterism and makes this stone the star of our gemstone jewellery collection too!
Sourced predominately in India, Star Diopside is a black to greenish-black calcium magnesium silicate (MgCaSi2O6) with a ranking of only 5.5 on MOH’s scale of hardness. Although a stunning choice for a ring this rock needs to be worn with caution.
Belonging to the monoclinic crystal system, diopside crystallises during the volcanic aftermath from the hot magma that has erupted from the Earth’s core. The mineral constituents within the molten lava cool slowly and begin to crystalise. Along with Diopside ingredients there is also Magnetite (iron oxide Fe3O4) and these small, elongated particles align at 180 degrees to one another throughout the diopside material in fine layers.
The result of this crystalline structure is a dense, silky, opaque gem that presents a white 2-rayed (four pointed) star when light is reflected off the polished stone’s surface. Best viewed when a stone is cut in cabochon, you’ll rarely see a ‘star’ stone in anything other than a round or oval shape.
Asterisms aren’t seen all too often and not all gemstones have the ability to show them. The main commercial stones that exhibit this phenomenon are Rubies and Sapphires (corundum) and the mineral inclusions that are responsible for their stars are Rutile needles (TiO2). They form at 120 degrees to each other creating a 3-rayed (six-pointed) star.
Bunny Bedi, owner and designer at Made in Earth, loves this starry-eyed beauty.
“It’s always been a favourite of mine and although it’s sourced almost exclusively from south India the locals don’t seem to know much about it.
“Like most gemstones, there are specialised stone cutters who have the skills and knowledge to gain the best cabs out of the rough. They ensure the star is centred and the surface is smooth and highly polished. Larger stones at a high quality are harder to get as they tend to be pitted and the stars are not as straight or clearly defined.”
The lure of the asterism can be enchanting and certainly a nice change from a flat and lifeless Onyx.