Characteristics of Obsidian:

Chemical Name: Silicon dioxide

Formula: Composed of SiO2, MgO and Fe3O4

Colors: Black, red, brown

Structure: Amorphous

Hardness: 5-6

Specific Gravity: 2.35-2.60

Refractive Index: 1.45-1.55

Lustre: Vitreous

Streak: White

Locations: Europe, North America, South America, Australasia, Japan

What is Obsidian? 

Obsidian is a natural volcanic glass that forms when lava solidifies so quickly that mineral crystals do not have time to grow. Technically, Obsidian can have any chemical composition, although it is usually the product of silica-rich magmas. It is typically jet-black; hematite contained within it can result in red and brown varieties, and the inclusions of tiny gas bubbles can create a golden sheen. In snowflake Obsidian, clusters of light-colored needle-like crystals of cristobalite on broken surfaces resemble snowflakes.