Cairncrossite is a rare strontium-calcium silicate that typically forms as delicate, pearly-white radiating aggregates. It is primarily found within the manganese-rich environments of the Kalahari Manganese Field, often appearing as distinct micro-crystals associated with other rare hydrothermal minerals.
Is this cairncrossite?
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 cairncrossite with a known reference. Cairncrossite sits at Mohs 3, 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 to pearly.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy crystals, radial aggregates.
Often confused with
Cairncrossite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside cairncrossite
Minerals reported to co-occur with cairncrossite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Sr₂Ca₆Na₂(Si₄O₁₀)₄(OH)₂(H₂O)₁₅₋₁₄
- Mohs hardness
- 3
- Density
- 2.50 g/cm³
- Streak
- White
- Luster
- Vitreous to pearly
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
- Crystal habit
- Platy crystals, radial aggregates
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Formed by metasomatic alteration of a carbonate-rich manganese deposit
Where rockhounds find cairncrossite
Classic worldwide localities
- Wessels Mine (Block 17), Kalahari Manganese Field, North Cape Province, South Africa
Field-hunting tip
Where it forms: Formed by metasomatic alteration of a carbonate-rich manganese deposit. If you start seeing manganoan richterite, manganoan sugilite, lizardite in float, you are in the right ground. Typical habit: platy crystals, radial aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cairncrossite?+
Where is cairncrossite found?+
What rocks look like cairncrossite?+
What minerals are found with cairncrossite?+
What kind of rock does cairncrossite form in?+
What is cairncrossite used for?+
Find cairncrossite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
