Obsidian Black Granite
Beyond that their similarities end.
Obsidian black granite. Obsidian is not a genuine mineral or rock it is a natural glass that contains microscopic mineral crystals. Properties of rock is another aspect for granite vs obsidian. Granite is available in black grey orange pink white colors whereas obsidian is available in black blue brown green orange red tan yellow colors. Very few samples are nearly colorless.
Iron and magnesium typically give the obsidian a dark brown to black color. The black obsidian is an ideal material in making opals to offer color contrasting background. In some stones the inclusion of small white radially clustered crystals of cristobalite in the black glass produce a blotchy or snowflake pattern snowflake obsidian. However medium strength of obsidian with 5 5 hardness creates durability concerns and the jewelry industry avoids its use as they apply diamonds and other gemstones.
Obsidian and granite are igneous rocks so called because they were formed from the molten magma of volcanoes. Appearance of granite is veined or pebbled and that of obsidian is shiny.