Bultfonteinite is a rare calcium silicate mineral primarily known from kimberlite pipes and contact-metamorphosed limestone deposits. It typically presents as attractive, radial, or globular white-to-pink clusters that are highly prized by systematic mineral collectors.
Is this bultfonteinite?
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 bultfonteinite with a known reference. Bultfonteinite sits at Mohs 4.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Bultfonteinite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Bultfonteinite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pink.
- 5Look at form & habitCrystal system: triclinic. Typical habit: radiating globular clusters, lath-like crystals, fibrous aggregates.
Often confused with
Bultfonteinite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads vitreous on Bultfonteinite and vitreous to silky on Pectolite.
How to tell apart: Luster reads vitreous on Bultfonteinite and vitreous to pearly on Apophyllite.
Often found alongside bultfonteinite
Minerals reported to co-occur with bultfonteinite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₄Si₂O₇(F,OH)₄·H₂O
- Mohs hardness
- 4.5
- Density
- 2.68 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Radiating Globular Clusters, Lath-like Crystals, Fibrous Aggregates
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Kimberlite Pipes, Contact Metamorphic Zones in Limestone
- Typical price
- $20-150 per specimen depending on crystal size and clarity
Where rockhounds find bultfonteinite
Classic worldwide localities
- Bultfontein Mine, Kimberley, South Africa
- Wessels Mine, Kalahari Manganese Field, South Africa
- Crestmore, California, USA
Field-hunting tip
Look in kimberlite pipes, contact metamorphic zones in limestone country — that is the host setting where bultfonteinite typically forms. If you start seeing calcite, apophyllite, gyrolite in float, you are in the right ground. Field specimens usually show a radiating globular clusters, lath-like crystals, fibrous aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bultfonteinite?+
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What rocks look like bultfonteinite?+
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Find bultfonteinite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
