RocksdayRocksday #1 · October 22, 2026
The answer was Amethyst
The purple variety of quartz. Its color comes from traces of iron combined with natural radiation, and it often lines the inside of large volcanic geodes.
The clues
- Type
- Mineral
- Color & luster
- Purple · Vitreous
- Mohs hardness
- 7
- Crystal system
- Trigonal
- Found in
- Rio Grande do Sul, Brazil; Artigas, Uruguay
How to recognize amethyst
- Purple, often deepest at the crystal tips.
- Hardness 7 — scratches glass.
- Grows as clusters of pointed crystals inside geodes.
- No cleavage; breaks with a glassy, curved fracture.
Did you know? The name comes from Greek amethystos, 'not drunk' — and heating amethyst turns it yellow, which is how most citrine on the market is made.