Rhodesite is a rare hydrous silicate that typically forms delicate, fibrous, or acicular sprays and radiating white balls. It is most commonly found as a late-stage crystallization in cavities within alkaline igneous rocks and basaltic environments. Collectors prize it for its unique, fragile structure, which requires careful handling to maintain the integrity of its sprays.
Is this rhodesite?
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 rhodesite with a known reference. Rhodesite sits at Mohs ~4, 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: silky.
- 4Match the color rangeCompare against the expected color range: silky white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: fibrous.
Often confused with
Rhodesite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Okenite is the harder of the two (Mohs 5 vs. ~4); luster reads silky on Rhodesite and vitreous to pearly on Okenite.
How to tell apart: Mesolite is the harder of the two (Mohs 5 vs. ~4); luster reads silky on Rhodesite and vitreous, silky when fibrous on Mesolite.
Often found alongside rhodesite
Minerals reported to co-occur with rhodesite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₂Ca₂Si₈O₁₉(H₂O)₅
- Mohs hardness
- ~4
- Density
- 2.27-2.36 g/cm³
- Colors
- Silky white
- Streak
- White
- Luster
- Silky
- Transparency
- Translucent to transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Fibrous
- Cleavage
- Good, {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a kimberlite pipe (Kimberley, South Africa); in a magadiite deposit localized in altered silicic lavas (Trinity Co., California, USA)
Where rockhounds find rhodesite
Classic worldwide localities
- Redding, Trinity Co., California, USA
- Bultfontein diamond mine, Kimberley, Cape Province, South Africa
- Zeilberg, near Maroldsweisach, Bavaria, Germany
- San Venanzo, near Terni, Lazio, Italy
Field-hunting tip
Where it forms: In a kimberlite pipe (Kimberley, South Africa); in a magadiite deposit localized in altered silicic lavas (Trinity Co., California, USA). If you start seeing mountainite, magadiite, montmorillonite in float, you are in the right ground. Typical habit: fibrous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify rhodesite?+
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What rocks look like rhodesite?+
What minerals are found with rhodesite?+
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Find rhodesite on the map
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