Gem from lava (8)

I believe the answer is:

obsidian

(Other definitions for obsidian that I've seen before include "Glass bottle may be in this" , "Dark glass-like rock" , "Dark glassy rock formed from lava" , "Dark volcanic rock" , "Volcanic glass-like rock" .)

I've seen this clue in The Sun.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.