Tephroite is a manganese-rich member of the olivine group typically found in metamorphosed manganese deposits. Collectors often look for its characteristic flesh-red or brownish-gray granular masses, which are frequently associated with fluorescent minerals like willemite at localities such as Franklin, New Jersey.
Is this tephroite?
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 tephroite with a known reference. Tephroite sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Tephroite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Tephroite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: reddish-brown, gray, olive-green, flesh-red.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive, granular, or rarely as short prismatic crystals.
Often confused with
Tephroite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside tephroite
Minerals reported to co-occur with tephroite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mn₂SiO₄
- Mohs hardness
- 6
- Density
- 4.1 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Massive, Granular, Or Rarely as Short Prismatic Crystals
- Cleavage
- Distinct On {010}
- Rarity
- Uncommon
- Uses
- Collector, Research
- Host rock
- Metamorphosed Manganese Ore Deposits
- Typical price
- $10-60 for small specimens, higher for rare crystal clusters
Where rockhounds find tephroite
2 mapped spotsClassic worldwide localities
- Franklin, New Jersey, USA
- Långban, Sweden
- Jakobsberg, Sweden
- Burra, South Australia
Field-hunting tip
Look in metamorphosed manganese ore deposits country — that is the host setting where tephroite typically forms. If you start seeing willemite, franklinite, zincite in float, you are in the right ground. Field specimens usually show a massive, granular, or rarely as short prismatic crystals habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in California, New Jersey — start trip planning there.
Common questions
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Find tephroite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
