Redondite is a variety of variscite that contains significant iron substituting for aluminum. It typically occurs as soft, earthy, or nodular masses in phosphate-rich environments, most notably found on the island of Redonda. Collectors often value it for its association with secondary phosphate mineral assemblages.
Is this redondite?
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 redondite with a known reference. Redondite sits at Mohs 3.5-4.5, 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: dull.
- 4Match the color rangeCompare against the expected color range: yellow, green, white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: massive, crusts, or nodular aggregates.
Often confused with
Redondite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads dull on Redondite and vitreous to waxy on Variscite.
How to tell apart: Luster reads dull on Redondite and vitreous on Strengite.
How to tell apart: Luster reads dull on Redondite and vitreous, dull to chalky when massive on Crandallite.
Often found alongside redondite
Minerals reported to co-occur with redondite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AlPO₄·2H₂O
- Mohs hardness
- 3.5-4.5
- Density
- 2.5-2.6 g/cm³
- Streak
- White
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Massive, crusts, or nodular aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Lapidary
- Host rock
- phosphate rock deposits
Where rockhounds find redondite
Classic worldwide localities
- Redonda
- Leeward Islands
Field-hunting tip
Where it forms: phosphate rock deposits. If you start seeing crandallite, variscite, strengite in float, you are in the right ground. Typical habit: massive, crusts, or nodular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify redondite?+
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What rocks look like redondite?+
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Find redondite on the map
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