Enter a clue or pattern or both:
The Clue
Relative of perlite (8 letter answer)
The Answer
OBSIDIAN
Tags
Notes
The answer OBSIDIAN is so rare that it appears less than once every 2500 puzzles.
Definition
OBSIDIAN as a noun:
1. acid or granitic glass formed by the rapid cooling of lava without crystallization; usually dark, but transparent in thin pieces