Glasslike rock (8)

I believe the answer is:

obsidian

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

I've seen this clue in The Times.

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.