Fukalite is a rare calcium silicate mineral primarily known from the Fuka mine in Japan. It typically occurs as white or colorless fibrous aggregates within contact metamorphic skarn zones, often associated with other rare silicate minerals.
Is this fukalite?
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 fukalite with a known reference. Fukalite sits at Mohs 4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Fukalite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Fukalite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pale yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: fibrous aggregates, radiating needles, granular masses.
Often confused with
Fukalite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Xonotlite is the harder of the two (Mohs 6-6.5 vs. 4); luster reads vitreous on Fukalite and pearly on Xonotlite.
How to tell apart: Fukalite is noticeably harder (Mohs 4 vs. 2.5); luster reads vitreous on Fukalite and pearly on Tobermorite.
Often found alongside fukalite
Minerals reported to co-occur with fukalite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₄Si₂O₆(OH,F)₂·nH₂O
- Mohs hardness
- 4
- Density
- 2.65 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Fibrous Aggregates, Radiating Needles, Granular Masses
- Cleavage
- Perfect in One Direction
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Skarn Deposits
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find fukalite
Classic worldwide localities
- Fuka, Okayama Prefecture, Japan
Field-hunting tip
Look in skarn deposits country — that is the host setting where fukalite typically forms. If you start seeing spurrite, gehlenite, foshagite in float, you are in the right ground. Field specimens usually show a fibrous aggregates, radiating needles, granular masses habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find fukalite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
