Crystals That Start With O
There are 8 crystals, rocks and gemstones in Gemdle that start with the letter O — each with a specimen photo, its Mohs hardness and a quick note on how to spot it. Tap any stone for the full identification guide.
Notable crystals that start with O
- Obsidian — Black, vitreous lustre, Mohs 5–6.
- Opal — White, subvitreous to waxy lustre, Mohs 5.5–6.
- Onyx — Black, vitreous, silky lustre, Mohs 6.5–7.
- Olivine — Green, vitreous lustre, Mohs 6.5–7.0.
- Orthoclase — White, vitreous, pearly on cleavage surfaces lustre, Mohs 6 (defining mineral).
- Orpiment — Yellow, resinous, pearly on cleavage surface lustre, Mohs 1.5–2.
- Oligoclase — White, vitreous lustre, Mohs 6 to 6.5.
- Okenite — White, vitreous, pearly lustre, Mohs –5.
All 8 stones beginning with O
Frequently asked questions
How many crystals start with the letter O?
Gemdle lists 8 crystals, rocks and gemstones beginning with O, including Obsidian, Opal, Onyx.
What is a well-known crystal that starts with O?
Obsidian is one of the most searched-for stones beginning with O. Obsidian is a naturally occurring volcanic glass formed when lava extruded from a volcano cools rapidly with minimal crystal growth.