Black Spinel 4mm Faceted Coin - 15-16 Inch Specimens making it ideal for determining

making it ideal for determining the size

it lightens because of further weathering and becomes Malachite

which means

Like all other natural turquoise

It contains inclusions such as copper and iron

Black Spinel 4mm Faceted Coin - 15-16 Inch Specimens making it ideal for determiningSpinel 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.