Gearksutite is a rare calcium aluminum fluoride mineral that often forms as chalky, white, earthy masses or crusts. It is typically found in altered cryolite-bearing pegmatites and hydrothermal veins, where it appears as a secondary mineral product of fluorite or cryolite alteration.
Is this gearksutite?
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 gearksutite with a known reference. Gearksutite sits at Mohs 2-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Gearksutite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Gearksutite typically shows a earthy luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, grayish.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, chalky, earthy, botryoidal, or powdery crusts.
Often confused with
Gearksutite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Luster reads earthy on Gearksutite and dull on Kaolinite.
How to tell apart: Luster reads earthy on Gearksutite and vitreous on Gibbsite.
How to tell apart: Luster reads earthy on Gearksutite and vitreous to greasy on Cryolite.
Often found alongside gearksutite
Minerals reported to co-occur with gearksutite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaAl(OH)F₄·H₂O
- Mohs hardness
- 2-3
- Density
- 2.7-2.8 g/cm³
- Streak
- White
- Luster
- Earthy
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Massive, Chalky, Earthy, Botryoidal, Or Powdery Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites, Hydrothermal Deposits
- Typical price
- $20-150 depending on specimen size and quality
Where rockhounds find gearksutite
Classic worldwide localities
- Greenland
- Colorado, USA
- Kazakhstan
- Tajikistan
Field-hunting tip
Look in granite pegmatites, hydrothermal deposits country — that is the host setting where gearksutite typically forms. If you start seeing cryolite, fluorite, siderite in float, you are in the right ground. Field specimens usually show a massive, chalky, earthy, botryoidal, or powdery crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify gearksutite?+
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How much is gearksutite worth?+
Is gearksutite safe to handle?+
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Find gearksutite on the map
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