Taniajacoite is a rare strontium calcium manganese silicate, typically dark green to blackish-green. It occurs in chemically weathered metamorphosed manganese ore. It was first described from N'Chwaning III mine, Kalahari manganese field, Northern Cape province, South Africa.
Is this taniajacoite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch taniajacoite with a known reference. Taniajacoite sits at Mohs 5-5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Taniajacoite leaves a very light brown streak.
- 3Read the lusterHold the specimen under a strong light. Taniajacoite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark green, blackish-green.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy crystals.
Often confused with
Taniajacoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Taniajacoite is noticeably harder (Mohs 5-5.5 vs. 4); streak differs, so Taniajacoite leaves very light brown, Austinite leaves white; luster reads vitreous on Taniajacoite and subadamantine to silky on Austinite.
How to tell apart: Streak differs, so Taniajacoite leaves very light brown, Conichalcite leaves light green.
All properties
- Chemical formula
- SrCaMn³⁺₂Si₄O₁₁(OH)₄·2H₂O
- Mohs hardness
- 5-5.5
- Density
- 3.05 g/cm³
- Colors
- Streak
- Very Light Brown
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Platy Crystals
- Cleavage
- Good On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins
Where rockhounds find taniajacoite
Classic worldwide localities
- N'Chwaning III mine, Northern Cape province, South Africa
Field-hunting tip
Look in hydrothermal veins country, the host setting where taniajacoite typically forms. If you start seeing arsenates, copper secondary minerals in float, you are in the right ground. Field specimens usually show a platy crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find taniajacoite on the map
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