Black Spinel 4mm Natural Round - 15-16 Inch Stone Type_Indigo Gabbro but also for industrial purposes

but also for industrial purposes from watch gears and scientific instruments to sandpaper and other abrasives

Distinctive for its purple-and-gray tones

When this combination crystallized

Historically

Turquoise is one of the oldest known gemstones

Black Spinel 4mm Natural Round - 15-16 Inch Stone Type_Indigo Gabbro but also for industrial purposesSpinel is a hard vitreous magnesium aluminum oxide, and comes in a range of other colors, but those varieties are transparent. Black Spinel not only has the dark color, but it is opaque as well, rendering its black especially deep and mysterious. Sometimes called the "Black Prince's Ruby" for its role in the English crown. It has been mistaken for ruby and sapphire at times, but can be distinguished by its structure and its lower relative hardness.