Crystal Black Coral

Chemical Formula

Mostly calcium carbonate

Color

White, Red, Orange, Pink, Gray, Black

Hardness

3 - 4

Crystal System

Amorphous

Refractive Index

1.48 - 1.65

SG

2.6 - 2.7

Transparency

Translucent to opaque

Double Refraction

-.172

Luster

Vitreous, waxy

Cleavage

None