Rhodizite is an exceptionally hard and rare borate mineral prized by collectors for its brilliant luster and often small, sharp dodecahedral crystals. It is primarily found in complex granite pegmatites and is notable for its historical confusion with similar-looking minerals like Danburite. Collectors typically look for specimens from Madagascar, which can exhibit high-quality, gemmy crystal forms.
Is this rhodizite?
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 rhodizite with a known reference. Rhodizite sits at Mohs 8-8.5, 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: vitreous to slightly adamantine.
- 4Match the color rangeCompare against the expected color range: white, colorless, grayish, yellow, yellowish white.
- 5Look at form & habitCrystal system: cubic. Typical habit: crystalline.
Often confused with
Rhodizite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Rhodizite is noticeably harder (Mohs 8-8.5 vs. 7-7.25).
How to tell apart: Diamond is the harder of the two (Mohs 10 vs. 8-8.5); streak differs, so Rhodizite leaves white, Diamond leaves colorless; luster reads vitreous to slightly adamantine on Rhodizite and adamantine to greasy on Diamond.
Often found alongside rhodizite
Minerals reported to co-occur with rhodizite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- KAl₄Be₅B₁₁O₂₈
- Mohs hardness
- 8-8.5
- Density
- 3.22-3.44 g/cm³
- Streak
- White
- Luster
- Vitreous to slightly adamantine
- Transparency
- Transparent to translucent
- Crystal system
- Cubic
- Crystal habit
- Crystalline
- Cleavage
- {111} and {111}, indistinct
- Rarity
- Rare
- Uses
- Collector, Gemstone
- Host rock
- A rare late-stage accessory mineral in alkali-rich granite pegmatites
Where rockhounds find rhodizite
Classic worldwide localities
- Found in the Animikie Red Ace pegmatite, near Pine River, Florence Co., Wisconsin, USA
- Found near Sarapulka and Shaitanka, Mursinka district, Ural Mountains, Russia
- Antandrokomby, near Mt. Bity, at Andasy, Besesitra, and Ifsina, Manandona Valley, Antsirabe district, Madagascar
- Fiakarandava, south of the Manandona Valley, Madagascar
- Ambatofinandrahana district, in the Ankarata Mountains, Madagascar
- Antsongombato, 25 km southwest of Mahaiza, Betafo district, Madagascar
Field-hunting tip
Where it forms: A rare late-stage accessory mineral in alkali-rich granite pegmatites. If you start seeing londonite, elbaite, spodumene in float, you are in the right ground. Typical habit: crystalline. Train your eye for that shape before scanning the outcrop.
Common questions
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Find rhodizite on the map
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