Truscottite is a rare calcium silicate mineral typically found in cavities of igneous rocks or contact metamorphic environments. It is most easily identified by its distinctive pearly luster and platy, often foliated or radiating crystal habit.
Is this truscottite?
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 truscottite with a known reference. Truscottite sits at Mohs 2.5-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Truscottite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Truscottite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: white, pale yellow, brownish.
- 5Look at form & habitCrystal system: trigonal. Typical habit: platy crystals, radial aggregates, foliated masses.
Often confused with
Truscottite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Okenite is the harder of the two (Mohs 4.5-5 vs. 2.5-3).
How to tell apart: Prehnite is the harder of the two (Mohs 6-6.5 vs. 2.5-3); luster reads pearly on Truscottite and vitreous on Prehnite.
Often found alongside truscottite
Minerals reported to co-occur with truscottite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₄Si₆O₁₅(OH)₂·H₂O
- Mohs hardness
- 2.5-3
- Density
- 2.44-2.50 g/cm³
- Colors
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Platy Crystals, Radial Aggregates, Foliated Masses
- Cleavage
- Perfect Basal
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Hydrothermal Veins in Igneous Rocks, Contact Metamorphic Zones
- Typical price
- $20-150 thumbnail specimens
Where rockhounds find truscottite
Classic worldwide localities
- Ubekendt Ejland, Greenland
- Nagyteteny, Hungary
- Khibiny Massif, Russia
- Skye, Scotland
Field-hunting tip
Look in hydrothermal veins in igneous rocks, contact metamorphic zones country — that is the host setting where truscottite typically forms. If you start seeing calcite, apophyllite, quartz in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates, foliated masses habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find truscottite on the map
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