Crystal Golden Black Obsidian

Category

Volcanic glass

Formula
(repeating unit)

70–75% SiO2,
plus MgO, Fe3O4

Identification

Color

Deep black or blackish green

Fracture

Conchoidal

Mohs scalehardness

5–6[1]

Luster

Vitreous

Specific gravity

~2.4[2]

Optical properties

Translucent

References

[3]