RocksdayBlack Tourmaline vs Hornblende
The quickest way to tell Black Tourmaline from Hornblende: Black Tourmaline is clearly harder: Mohs 7–7.5 versus 5–6.
Schorl, the iron tourmaline and the most common species of the group. Opaque black prisms with a triangular cross-section.
Photo: Parent Géry, CC BY-SA 3.0
A common black amphibole and the dark specks in many granites and diorites.
Photo: Shannon Heinle, CC0
Quick tests
- Hardness: Black Tourmaline is clearly harder: Mohs 7–7.5 versus 5–6.
- Streak (rub on unglazed porcelain): Black Tourmaline leaves a white streak; Hornblende leaves gray-green.
Key differences
- Hornblende has two cleavages and is not as hard.
Side by side
| Property | Black Tourmaline | Hornblende |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 7–7.5 | 5–6 |
| Luster | Vitreous | Vitreous |
| Streak | White | Gray-green |
| Colors | Black | Black, Green, Brown |
| Crystal system | Trigonal | Monoclinic |
| Specific gravity | 3.1–3.25 | 3–3.4 |
| Formula | NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄ | Ca₂(Mg,Fe,Al)₅(Al,Si)₈O₂₂(OH)₂ |
| Found in | Erongo, Namibia; Minas Gerais, Brazil | Granites and diorites worldwide; Amphibolites |
Properties that are the same for both are grayed out.
How to identify black tourmaline
- Black prisms with lengthwise grooves.
- A broken end is a rounded triangle, not a circle.
- Hard — scratches glass. White streak, not black.
- No cleavage. A magnet does not stick.
Crystal system: Trigonal
Full Black Tourmaline guide →How to identify hornblende
- Black to dark green elongated prisms.
- Two cleavages meeting at about 56° and 124°.
- Shiny, splintery breaks.
Crystal system: Monoclinic
Full Hornblende guide →More comparisons
Frequently asked questions
What is the difference between black tourmaline and hornblende?
Black Tourmaline is a mineral with a Mohs hardness of 7–7.5 and a vitreous luster, usually black. Hornblende is a mineral with a Mohs hardness of 5–6 and a vitreous luster, usually black, green or brown.
How can you tell black tourmaline from hornblende?
Black Tourmaline is clearly harder: Mohs 7–7.5 versus 5–6. Black Tourmaline leaves a white streak; Hornblende leaves gray-green. Hornblende has two cleavages and is not as hard.
Could you tell them apart from a blurry close-up?
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