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. Wiluite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Wiluite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow, green, brown.
- 5Look at form & habitCrystal system: tetragonal. Typical habit: prismatic 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
- Ca₁₉Mg₃Al₄(B,Al,Fe)₅Si₁₈O₆₉(OH,O)₉
- Mohs hardness
- 6
- Density
- 3.37-3.41 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Tetragonal
- Crystal habit
- Prismatic Crystals
- Cleavage
- Poor
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Contact Metamorphosed Limestone
- Typical price
- $20-150 for thumbnail to small cabinet specimens
Where rockhounds find wiluite
Classic worldwide localities
- Wilui River, Sakha Republic, Russia
- Holt Quarry, Quebec, Canada
- Eden Mills, Vermont, USA
Field-hunting tip
Look in contact metamorphosed limestone country, the host setting where wiluite typically forms. If you start seeing grossular, diopside, calcite in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so 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.
