It is a rarity but some Obsidian has been found with small Gas Bubbles in it which when chipped or broken it can have cavities. the Natural Museum in San Francisco, California, has been known to have some Samples for Viewing and study.
Obsidian is a naturally occurring volcanic form of glass.
Obsidian
No. Obsidian is brittle.
Mahogany Obsidian
No. Obsidian is natural glass, mostly silica. Obsidian is of volcanic origin.
Obsidian is, itself, a mineral.
Obsidian is a natural glass.
Neither, obsidian is a glass.
yes obsidian is a crystal.
Obsidian is an igneous rock.
Other names for obsidian is Apache tears, volcanic glass, and Black obsidian.
Snowflake Obsidian