Identification & care guide
Black Tourmaline vs Obsidian: 8 Ways to Tell Them Apart
Black tourmaline and black obsidian can look similar after polishing, but one is a crystalline mineral and the other is natural volcanic glass. Raw surfaces usually reveal the difference fastest.
Mineral versus volcanic glass
Black tourmaline sold in crystal shops is commonly schorl, a borosilicate mineral. Obsidian forms when silica-rich lava cools too quickly to build an orderly crystal structure. That difference controls their surface features and breakage.
Search for lengthwise striations
Schorl commonly forms elongated prisms with strong parallel grooves running along the crystal. Broken bundles may show several joined columns. Obsidian does not grow prismatic crystals and will not have true crystal-growth striations.
Inspect existing broken surfaces
Obsidian typically breaks with smooth, curved conchoidal surfaces and can form extremely sharp edges. Tourmaline is also brittle, but rough pieces usually retain a more granular, splintery, or columnar structure. Never create a new break for testing.
Compare luster and polished appearance
Fresh obsidian often has a uniformly glassy luster and may show flow bands, snowflake-like inclusions, or a golden or rainbow sheen. Tourmaline can be glassy on crystal faces but rougher in grooves and across broken ends.
Check thin edges for transmitted light
Many black tourmaline pieces remain opaque even at thin edges, although some tourmalines can transmit brownish or greenish light. Thin obsidian edges may transmit smoky brown light. Thickness and lighting matter, so this is a supporting clue only.
Understand the hardness gap
Tourmaline is commonly around Mohs 7 to 7.5, while obsidian is roughly Mohs 5 to 5.5. The gap affects scratch resistance, but a scratch test is unnecessary and can permanently mark polished material.
Handle both as brittle
Hardness does not prevent breakage. Cushion tourmaline terminations and keep obsidian away from impacts that can create razor-sharp chips. Store each piece separately rather than loose with harder quartz.
Know the common look-alikes
Onyx, dyed agate, jet, slag glass, black spinel, and molded glass may be sold under broad black-stone labels. If crystal habit and provenance are missing, use a gemologist for valuable jewelry or collector material.
At-a-glance reference
| Feature | Black tourmaline / schorl | Obsidian |
|---|---|---|
| Material | Crystalline borosilicate mineral | Natural volcanic glass |
| Typical texture | Prismatic, columnar, strongly striated | Smooth, glassy, sometimes flow banded |
| Breakage | Brittle; may look splintery or granular | Curved conchoidal fracture; very sharp chips |
| Mohs hardness | About 7–7.5 | About 5–5.5 |
| Thin-edge light | Usually opaque; sometimes brownish or greenish | May transmit smoky brown light |
| Storage | Cushion points and grooves | Protect from impacts and harder stones |
Frequently asked questions
Which is shinier, tourmaline or obsidian?
Fresh obsidian is often uniformly glassy. Tourmaline can be glassy on faces but commonly looks rougher inside its lengthwise grooves.
Can black tourmaline scratch obsidian?
Tourmaline is generally harder and could abrade obsidian during repeated contact, especially with pressure or trapped grit.
Is snowflake obsidian tourmaline?
No. Snowflake obsidian is volcanic glass containing pale spherulitic structures, not tourmaline crystals.
Reference databases
Property and care guidance is checked against established mineralogical and gemological references. See our sources and methodology.