RocksdayBlack Tourmaline vs Neptunite
The quickest way to tell Black Tourmaline from Neptunite: 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
Black prisms that are deep red on thin edges, famous on white natrolite beside blue benitoite.
Photo: Géry PARENT, Public domain
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; Neptunite leaves reddish brown.
Key differences
- Schorl is harder, has a white streak and a triangular cross-section.
Side by side
| Property | Black Tourmaline | Neptunite |
|---|---|---|
| Type | Mineral | Mineral |
| Mohs hardness | 7–7.5 | 5–6 |
| Luster | Vitreous | Vitreous |
| Streak | White | Reddish brown |
| Colors | Black | Black, Red |
| Crystal system | Trigonal | Monoclinic |
| Specific gravity | 3.1–3.25 | 3.2–3.3 |
| Formula | NaFe₃Al₆(BO₃)₃Si₆O₁₈(OH)₄ | KNa₂Li(Fe,Mn)₂Ti₂Si₈O₂₄ |
| Found in | Erongo, Namibia; Minas Gerais, Brazil | San Benito County, California; Kola Peninsula, Russia |
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 neptunite
- Square-ish black prisms; thin edges glow red.
- Reddish-brown streak.
- Hardness about 5–6.
Crystal system: Monoclinic
Full Neptunite guide →More comparisons
Frequently asked questions
What is the difference between black tourmaline and neptunite?
Black Tourmaline is a mineral with a Mohs hardness of 7–7.5 and a vitreous luster, usually black. Neptunite is a mineral with a Mohs hardness of 5–6 and a vitreous luster, usually black or red.
How can you tell black tourmaline from neptunite?
Black Tourmaline is clearly harder: Mohs 7–7.5 versus 5–6. Black Tourmaline leaves a white streak; Neptunite leaves reddish brown. Schorl is harder, has a white streak and a triangular cross-section.
Could you tell them apart from a blurry close-up?
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