Wiluite is a rare borosilicate mineral that is structurally related to vesuvianite, often appearing as distinct, lustrous yellow-green to brown prismatic crystals. It is primarily found in contact metamorphic zones where boron-rich fluids have interacted with limestone. Collectors highly prize these crystals for their sharp tetragonal habit and distinct chemical composition compared to common vesuvianite.
Is this wiluite?
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 wiluite with a known reference. Wiluite sits at Mohs 6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: colorless.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: dark green.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: euhedral crystals.
Often confused with
Wiluite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside wiluite
Minerals reported to co-occur with wiluite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₁₉(Al,Mg)₁₃(B,□,Al)₅(SiO₄)₁₀(Si₂O₇)₄(O,OH)₁₀
- Mohs hardness
- 6
- Density
- 3.36 g/cm³
- Colors
- Streak
- Colorless
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Euhedral crystals
- Cleavage
- Poor on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In metasomatized skarn (Russia)
Where rockhounds find wiluite
Classic worldwide localities
- Bill Waley mine, Tulare County, California, USA
- Templeton Township, Quebec, Canada
- Ignimbrite quarry of Parco Chigi, Ariccia community, Rome, Latium, Italy
Field-hunting tip
Where it forms: In metasomatized skarn (Russia). If you start seeing grossular, serpentine minerals, carbonate in float, you are in the right ground. Typical habit: euhedral crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find wiluite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
