Delhayelite is a rare silicate mineral primarily found in volcanic alkaline rocks, notably as a constituent of the lavas of Mount Nyiragongo. It typically forms thin, platy crystals or radial clusters that can be difficult to distinguish from associated feldspathoids without analytical testing.
Is this delhayelite?
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 delhayelite with a known reference. Delhayelite sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Delhayelite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Delhayelite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, pale yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy crystals, radial aggregates.
Often confused with
Delhayelite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside delhayelite
Minerals reported to co-occur with delhayelite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Na,K)₁₀Ca₂Al₆Si₁₂O₃₅(OH,F,Cl)₂
- Mohs hardness
- 3-4
- Density
- 2.36 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy Crystals, Radial Aggregates
- Cleavage
- Good On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Rocks
- Typical price
- $50-300 per specimen
Where rockhounds find delhayelite
Classic worldwide localities
- Mount Nyiragongo, Democratic Republic of the Congo
- Kola Peninsula, Russia
Field-hunting tip
Look in alkaline igneous rocks country — that is the host setting where delhayelite typically forms. If you start seeing nepheline, leucite, melilite in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find delhayelite on the map
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