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 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: vitreous.
- 4Match the color rangeCompare against the expected color range: colorless, greenish gray, light gray green.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: platy.
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
- K₇Na₃Ca₅Al₂Si₁₄O₃₈F₄Cl₂
- Mohs hardness
- 4-5
- Density
- 2.60 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Orthorhombic
- Crystal habit
- Platy
- Cleavage
- Distinct on {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a kalsilite-bearing melilite-nepheline lava (Mt. Shaheru, Congo)
Where rockhounds find delhayelite
Classic worldwide localities
- Mt. Shaheru, the extinct southern cone of Mt. Nyiragongo, Kivu Province, Congo (Zaire)
- Mts. Rasvumchorr and Yukspor, Khibiny massif, Kola Penninsula, Russia
Field-hunting tip
Where it forms: In a kalsilite-bearing melilite-nepheline lava (Mt. Shaheru, Congo). If you start seeing kalsilite, nepheline, götzenite in float, you are in the right ground. Typical habit: platy. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify delhayelite?+
Where is delhayelite found?+
What rocks look like delhayelite?+
What minerals are found with delhayelite?+
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What is delhayelite used for?+
Find delhayelite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
