Ternesite is a rare calcium silicate sulfate mineral typically found in combustion metamorphic settings or within high-temperature industrial slags. It usually occurs as small, colorless to pale yellow prismatic crystals that can be difficult to distinguish from common sulfates without chemical testing.
Is this ternesite?
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 ternesite with a known reference. Ternesite sits at Mohs 3.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ternesite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Ternesite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, pale yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: prismatic crystals, acicular, granular.
Often confused with
Ternesite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside ternesite
Minerals reported to co-occur with ternesite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₅(SiO₄)₂(SO₄)
- Mohs hardness
- 3.5
- Density
- 3.48 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Prismatic Crystals, Acicular, Granular
- Cleavage
- Distinct On {010}
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Metamorphic Rocks Formed By Combustion of Bituminous Sediments
- Typical price
- $50-300 per specimen
Where rockhounds find ternesite
Classic worldwide localities
- Ettringer Bellerberg, Germany
- Hatrurim Basin, Israel
- Jordansmühl, Poland
Field-hunting tip
Look in metamorphic rocks formed by combustion of bituminous sediments country — that is the host setting where ternesite typically forms. If you start seeing ettringite, portlandite, afwillite in float, you are in the right ground. Field specimens usually show a prismatic crystals, acicular, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find ternesite on the map
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