As with other forms of obsidian, rainbow obsidian is both rock and glass. However, ... This molten earth origin is what classes rainbow obsidian as an igneous rock.

glass, obsidian, igneous rocks. Facebook Facebook. Reddit. Flipboard. Envelope. Discuss (0 CommentS) FOLLOW ON NEWS. More Nature Stories. link to article “It Shoots ...

The author freely admits the difficulty that arises in the case of the glassy rocks and suggests that the ‘norms’ may be of service here. A Descriptive Petrography of the Igneous Rocks. By ...

A DISCUSSION on the origin of igneous rocks was held in Section C (Geology) of the British Association at York on September 7. The discussion was opened by Prof. Arthur Holmes, who sketched out a ...