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, 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?+
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Find gearksutite on the map
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