Re: Obsidian glass.
Just a guess (from an Earthly perspective):
Mono Craters and Obsidian (black/dark lava glass). Another link from the same source.
Space/Science » in reply to Re: Here in Oxia Palus for example
Just a guess (from an Earthly perspective):
Mono Craters and Obsidian (black/dark lava glass). Another link from the same source.