Povondraite Identification Guide
How to identify povondraite, a rare iron-rich tourmaline, by its dark reddish-brown to black color, striated prisms, hardness, and how to separate it from schorl and dravite.
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What Povondraite Looks Like
Povondraite is a rare sodium-iron-rich member of the tourmaline group (an oxy-tourmaline with ferric iron). It is typically dark reddish-brown, brownish-black, or black, sometimes showing a reddish internal color in thin splinters or under strong light. Luster is vitreous to submetallic, and crystals are opaque to translucent. Like all tourmalines, it forms prismatic crystals with a rounded triangular cross-section and strong lengthwise striations.
Step-by-Step Field ID Checklist
- Recognize tourmaline form. Look for prismatic crystals with a rounded triangular cross-section and parallel striations down the length.
- Note the dark reddish-brown color. Reddish-brown to black with a possible red internal hue hints at the iron-rich povondraite end.
- Check for no cleavage. Tourmaline fractures conchoidally; cleavage is essentially absent.
- Test hardness. Scratches glass and steel readily.
- Consider the setting. Povondraite forms in evaporite-related metamorphic and borate-rich settings — locality is a strong clue.
Key Diagnostic Tests
- Mohs hardness: 7 to 7.5 — scratches quartz.
- Cleavage: None to very poor; uneven to conchoidal fracture.
- Streak: White to pale brown.
- Specific gravity: About 3.1 to 3.3 (relatively high for tourmaline, due to iron).
- Pleochroism: Present but often masked by dark color.
- Crystal form: Trigonal prisms, rounded triangular section, striated.
Common Look-Alikes and How to Tell Them Apart
- Schorl (black tourmaline): Visually very similar dark tourmaline; povondraite is more reddish-brown and is the oxidized iron-rich, boron-rich species. Reliable separation usually needs chemical/optical analysis.
- Dravite (brown tourmaline): Magnesium-rich brown tourmaline; povondraite is iron-rich and typically darker/redder. Lab work distinguishes them.
- Hornblende/black amphibole: Has two cleavages at ~56/124 degrees, unlike tourmaline's lack of cleavage and striated prisms.
- Black garnet (melanite): Isometric, no prisms or striations, no pleochroism.
- Magnetite: Magnetic, metallic, with octahedral form; tourmaline is not magnetic and is harder.
Where Povondraite Is Found
Povondraite was first described from the Alto Chapare region, Cochabamba, Bolivia, in metamorphosed evaporite/borate-bearing rocks. It is rare and occurs in similar boron-rich metasedimentary settings elsewhere; most specimens trace to the Bolivian type locality.
Frequently asked questions
What is povondraite?
Povondraite is a rare iron-rich, oxidized member of the tourmaline group (an oxy-tourmaline), typically dark reddish-brown to black, first described from Bolivia.
How can you tell if it's real povondraite?
Look for dark reddish-brown to black tourmaline prisms with a rounded triangular cross-section, lengthwise striations, hardness 7 to 7.5, no cleavage, and relatively high density. Distinguishing it from schorl usually needs lab analysis.
Povondraite vs schorl: what is the difference?
Both are dark tourmalines, but povondraite is an oxidized iron-and-boron-rich species, often more reddish-brown, while schorl is the common black iron tourmaline; chemical analysis is the reliable separator.
Is povondraite magnetic?
No. Despite its iron content, povondraite is not magnetic, which helps separate it from magnetite and other metallic iron minerals.