Tacharanite is a rare calcium silicate mineral typically found as white, platy, or scaly aggregates within basalt cavities. It is often discovered in association with other zeolite-group minerals and calcium silicates in altered volcanic environments. Collectors prize it for its specific paragenesis within restricted geological sites like the Isle of Skye.
Is this tacharanite?
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 tacharanite with a known reference. Tacharanite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Tacharanite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Tacharanite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pale yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy aggregates, scaly masses.
Often confused with
Tacharanite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside tacharanite
Minerals reported to co-occur with tacharanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₁₂Al₂Si₁₈O₅₇(OH)₁₀·~4H₂O
- Mohs hardness
- 3-4
- Density
- 2.45 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Aggregates, Scaly Masses
- Cleavage
- Perfect in One Direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Basaltic Volcanic Rocks
- Typical price
- $20-100 per specimen
Where rockhounds find tacharanite
Classic worldwide localities
- Skye, Scotland
- Antrim, Northern Ireland
- Fuka, Japan
Field-hunting tip
Look in basaltic volcanic rocks country — that is the host setting where tacharanite typically forms. If you start seeing tobermorite, gyrolite, calcite in float, you are in the right ground. Field specimens usually show a platy aggregates, scaly masses habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find tacharanite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
