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, 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.
