RocksdayOlivine vs Tourmaline
How to tell them apart
Olive-green silicate that makes up most of Earth's upper mantle. Gem-quality olivine is called peridot.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
A boron-bearing silicate found in more colors than almost any other gem. Black schorl is the most common form.
Photo: Robert M. Lavinsky, CC BY-SA 3.0
Key differences
- Green tourmaline grows in long prisms with triangular cross-sections.
- Olivine forms grains, not long striated prisms.
Side by side
| Property | Olivine | Tourmaline |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 6.5–7 | 7–7.5 |
| Luster | Vitreous | Vitreous |
| Streak | White | White |
| Colors | Green, Yellow | Black, Green, Pink |
| Crystal system | Orthorhombic | Trigonal |
| Specific gravity | 3.2–4.4 | 3–3.3 |
| Formula | (Mg,Fe)₂SiO₄ | Complex borosilicate |
| Found in | Papakōlea, Hawaii; San Carlos, Arizona | Mount Mica, Maine; San Diego County, California |
Properties that are the same for both are grayed out.
How to identify olivine
- Bottle- to olive-green glassy grains.
- Often as sugary green clumps in black basalt.
- No cleavage — breaks like glass.
- Hard enough to scratch glass.
Crystal system: Orthorhombic
Full Olivine guide →How to identify tourmaline
- Long prisms with lengthwise grooves (striations).
- Rounded-triangle cross-section when broken across.
- Hard — scratches glass.
- Gem crystals can change color from end to end ('watermelon').
Crystal system: Trigonal
Full Tourmaline guide →More comparisons
Could you tell them apart from a blurry close-up?
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