Black Spinel 4mm Faceted Coin - 15-16 Inch Specimens midnight blue glass with flecks

midnight blue glass with flecks of copper suspended within it

and pattern

making it ideal for determining the size

but it is not true

it lightens because of further weathering and becomes Malachite

Black Spinel 4mm Faceted Coin - 15-16 Inch Specimens midnight blue glass with flecksSpinel 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.