Imayoshiite is an extremely rare calcium aluminum borosilicate mineral known primarily from the Fuka Mine in Japan. It typically occurs as small, colorless, prismatic crystals within skarn environments associated with high-temperature contact metamorphism of limestone.
Is this imayoshiite?
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 imayoshiite with a known reference. Imayoshiite sits at Mohs 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous (crystals); silky (aggregates).
- 4Match the color rangeCompare against the expected color range: colorless crystals.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: prismatic crystals.
Often confused with
Imayoshiite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside imayoshiite
Minerals reported to co-occur with imayoshiite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₃Al(CO₃)[B(OH)₄](OH)₆·12H₂O
- Mohs hardness
- 2-3
- Density
- 1.79 g/cm³
- Colors
- Colorless crystals
- Streak
- White
- Luster
- Vitreous (crystals); silky (aggregates)
- Transparency
- Transparent
- Crystal system
- Hexagonal
- Crystal habit
- Prismatic crystals
- Cleavage
- Distinct on {101̄0}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In cavities in an altered gabbro xenolith in serpentinized dunite, where rims of the xenoliths were hydrothermally altered
Where rockhounds find imayoshiite
Classic worldwide localities
- Suisho-dani valley, Ise City, Mie Prefecture, Japan
Field-hunting tip
Where it forms: In cavities in an altered gabbro xenolith in serpentinized dunite, where rims of the xenoliths were hydrothermally altered. If you start seeing oyelite, xonotlite, tobermorite in float, you are in the right ground. Typical habit: prismatic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify imayoshiite?+
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What rocks look like imayoshiite?+
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Find imayoshiite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
