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. Streak: very light brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 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: Streak differs, so Taniajacoite leaves very light brown, Austinite leaves white; luster reads vitreous on Taniajacoite and subadamantine to silky in aggregates on Austinite.
How to tell apart: Streak differs, so Taniajacoite leaves very light brown, Conichalcite leaves green.
Often found alongside taniajacoite
Minerals reported to co-occur with taniajacoite. Spotting these in float or country rock is a strong cue you are in the right ground.
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
- On chemically weathered metamorphosed manganese ore
Where rockhounds find taniajacoite
Classic worldwide localities
- N’Chwaning III mine, Kalahari manganese field, Northern Cape province, South Africa
Field-hunting tip
Where it forms: On chemically weathered metamorphosed manganese ore. If you start seeing sugilite, aegirine, pectolite in float, you are in the right ground. Typical habit: platy crystals. 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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