Falcondoite is a rare nickel-rich member of the sepiolite group, typically appearing as a vibrant green or pale green massive material. It is primarily found as a weathering product in nickel-bearing lateritic soils and is highly valued by mineral collectors specializing in rare secondary nickel species.
Is this falcondoite?
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 falcondoite with a known reference. Falcondoite 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. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: resinous.
- 4Match the color rangeCompare against the expected color range: green, yellowish green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: fibrous, microscopic crystals.
Often confused with
Falcondoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Chrysoprase is the harder of the two (Mohs 6.5-7 vs. 2-3); luster reads resinous on Falcondoite and vitreous to waxy on Chrysoprase.
How to tell apart: Luster reads resinous on Falcondoite and dull on Sepiolite.
Often found alongside falcondoite
Minerals reported to co-occur with falcondoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ni₄Si₆O₁₅(OH)₂·6H₂O
- Mohs hardness
- 2-3
- Density
- 1.9 g/cm³
- Colors
- Streak
- White
- Luster
- Resinous
- Transparency
- Transparent to translucent
- Crystal system
- Orthorhombic
- Crystal habit
- Fibrous, microscopic crystals
- Cleavage
- Distinct
- Rarity
- Rare
- Uses
- Collector, Ore mineral
- Host rock
- In garnierite veins which cut an extensive laterite, associated with a serpentinized harzburgite massif (near Bonao, Dominican Republic)
Where rockhounds find falcondoite
Classic worldwide localities
- Glamis, Imperial Co., California, USA
- Bonao, Dominican Republic
Field-hunting tip
Where it forms: In garnierite veins which cut an extensive laterite, associated with a serpentinized harzburgite massif (near Bonao, Dominican Republic). If you start seeing sepiolite, talc, quartz in float, you are in the right ground. Typical habit: fibrous, microscopic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find falcondoite on the map
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