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. Cairncrossite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Cairncrossite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: orthorhombic. 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
- (Sr,Ca)₁₄(Si₄O₁₀)₂(Si₂O₇)(OH)₄·~20H₂O
- Mohs hardness
- 3
- Density
- 2.16 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy Crystals, Radial Aggregates
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Hydrothermal Veins in Manganese Ore Deposits
- Typical price
- $50-300 per specimen
Where rockhounds find cairncrossite
Classic worldwide localities
- Kalahari Manganese Field, South Africa
Field-hunting tip
Look in hydrothermal veins in manganese ore deposits country, the host setting where cairncrossite typically forms. If you start seeing manganite, hausmannite, calcite in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify cairncrossite?+
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How much is cairncrossite worth?+
What rocks look like cairncrossite?+
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Find cairncrossite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
