Brown Tourmaline Identification Guide
Identifying brown tourmaline (dravite), a magnesium-rich tourmaline, by its striated prisms, pleochroism, hardness, and look-alikes.
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What Brown Tourmaline Looks Like
Brown tourmaline is most often dravite, the magnesium-rich member of the tourmaline group, colored brown to yellow-brown, coffee, and reddish-brown by iron and titanium. Crystals are transparent to translucent or opaque, with a vitreous luster. A hallmark of tourmaline is strong pleochroism—the stone looks markedly darker down the long axis (c-axis) than across it.
Crystal habit / form
Tourmaline forms elongated prismatic crystals with a rounded-triangular cross-section and strong lengthwise striations on the prism faces. Crystal terminations are often different at each end (hemimorphism). These striated, three-sided prisms are the single best field clue.
Step-by-Step Field ID Checklist
- Look at the cross-section. A rounded triangular outline is classic tourmaline.
- Check for striations running the length of the prism faces.
- Test pleochroism. View along vs across the crystal—brown tourmaline darkens noticeably down its length.
- Test hardness. Mohs ~7–7.5; scratches glass and quartz with effort.
- Examine fracture. Uneven to conchoidal, with no good cleavage (tourmaline cleavage is poor).
- Check the streak. White.
Key Diagnostic Tests
- Mohs hardness: ~7–7.5. Scratches glass readily; resists a knife.
- Streak: White.
- Cleavage: Indistinct/poor—tourmaline characteristically lacks easy cleavage; relies on hardness and habit.
- Pleochroism: Strong—diagnostic for tourmaline.
- Density: ~3.0–3.2 g/cm³.
- Pyroelectric/piezoelectric: Tourmaline can attract dust/paper when warmed or rubbed—a classic confirming trait.
Common Look-Alikes and How to Tell Them Apart
- Brown quartz (smoky): No striated triangular prisms; six-sided crystals with horizontal striations and clear single termination, and weaker pleochroism.
- Andalusite: Strong pleochroism too, but squarish cross-section and distinct cleavage; lower density.
- Brown zircon: Much denser (~4.6), higher luster and dispersion, tetragonal habit.
- Axinite: Brown and glassy but forms sharp wedge-shaped crystals with good cleavage.
- Bronzite/enstatite: Has ~90° cleavage and a bronze sheen; tourmaline lacks cleavage and shows triangular prisms.
Where It Is Found
Dravite and brown tourmaline occur in metamorphosed limestones, schists, and magnesium-rich rocks, plus granitic pegmatites. Notable sources include Australia (Yinnietharra, the type area for dravite at Dravograd is in Slovenia), Brazil, Tanzania (Kenya/Tanzania border), Sri Lanka, and the United States. Gem-quality brown tourmaline is faceted, while opaque crystals are popular mineral specimens.
Frequently asked questions
How can you tell if it's real brown tourmaline?
Real brown tourmaline shows elongated prisms with a rounded-triangular cross-section, strong lengthwise striations, strong pleochroism (darker down the length), hardness 7–7.5, a white streak, and poor cleavage. It can also attract dust when warmed (pyroelectricity).
What is brown tourmaline called?
Brown tourmaline is usually dravite, the magnesium-rich species of the tourmaline group, though iron-bearing schorl can also appear brownish.
Brown tourmaline vs smoky quartz—how do I tell them apart?
Tourmaline forms triangular-section prisms with lengthwise striations and strong pleochroism, while smoky quartz forms six-sided prisms with horizontal striations and weak pleochroism. Both are about Mohs 7.
What does brown tourmaline look like?
It appears as brown to coffee or reddish-brown elongated crystals with glassy luster and ribbed (striated) faces, often noticeably darker when viewed end-on than from the side.