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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: 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.
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
- 2.73 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Radiating globular clusters, lath-like crystals, fibrous aggregates
- Cleavage
- Good on {100} and {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a large horse of diabase and shale fragments in a kimberlite pipe (Bultfontein mine, Kimberley, South Africa); in a contact zone in thermally metamorphosed limestone (Crestmore, California, USA)
Where rockhounds find bultfonteinite
Classic worldwide localities
- Crestmore, Riverside Co., California, USA
- Cape Province, in the Bultfontein and Dutoitspan diamond mines, Kimberley, South Africa
- Jagersfontein diamond mine, Orange River Colony, South Africa
- N'Chwaning and Wessels manganese mines, near Kuruman, South Africa
- Hatrurim Formation, Israel
- Fuka, near Bicchu, and in the Mihara mine, Okayama Prefecture, Japan
Field-hunting tip
Where it forms: In a large horse of diabase and shale fragments in a kimberlite pipe (Bultfontein mine, Kimberley, South Africa); in a contact zone in thermally metamorphosed limestone (Crestmore, California, USA). If you start seeing calcite, apophyllite, natrolite in float, you are in the right ground. Typical habit: radiating globular clusters, lath-like crystals, fibrous aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bultfonteinite?+
Where is bultfonteinite found?+
What rocks look like bultfonteinite?+
What minerals are found with bultfonteinite?+
What kind of rock does bultfonteinite form in?+
What is bultfonteinite used for?+
Find bultfonteinite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
