Why Is Obsidian Black?

Obsidian is usually black. This color is caused by minute inclusions and tiny crystals in the glass. Red color is caused by the same stuff that gives red color to weathered basalt, desert sand and K-feldspar. ... Obsidian is usually dark and its surface is shiny.

Why is obsidian black if it is felsic?

Obsidian is commonly a translucent dark brown or black. Unlike basalt, obsidian's dark color is due to high amounts of impurities rather than the presence of dark colored minerals. The color of obsidian depends on the chemical composition of the impurities.

Is obsidian a black color?

Though obsidian is typically jet-black in colour, the presence of hematite (iron oxide) produces red and brown varieties, and the inclusion of tiny gas bubbles may create a golden sheen. Other types with dark bands or mottling in gray, green, or yellow are also known.