Dalyite is a rare potassium-zirconium silicate mineral typically found in peralkaline igneous complexes. It usually appears as small, colorless, or pale yellow tabular crystals embedded in alkaline rocks like granite or syenite. Collectors prize it for its unique chemistry and strictly defined geological occurrence in specialized volcanic environments.
Is this dalyite?
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 dalyite with a known reference. Dalyite sits at Mohs 7.5, 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.
- 5Look at form & habitCrystal system: triclinic. Typical habit: tabular crystals, subhedral grains.
Often confused with
Dalyite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside dalyite
Minerals reported to co-occur with dalyite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- K₂ZrSi₆O₁₅
- Mohs hardness
- 7.5
- Density
- 2.84 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Tabular crystals, subhedral grains
- Cleavage
- Distinct on {101} and {010}, indistinct on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare accessory in ejected blocks of alkalic granite in trachytic and basaltic tuffs (Ascension Island); in syenite (Serra de Agua de Pau, Azores); in lamproite (Cancarix, Spain)
Where rockhounds find dalyite
Classic worldwide localities
- Green Mountain and Middleton Peak, Ascension Island, southern Atlantic Ocean
- Serra de Agua de Pau, São Miguel, Azores
- Cancarix, Albacete Province, Spain
- Dalsfjorden, Sunnfjord, and Gjerdingen, near Oslo, Norway
- Straumsvola complex, Dronning Maud Land, Antarctica
Field-hunting tip
Where it forms: A rare accessory in ejected blocks of alkalic granite in trachytic and basaltic tuffs (Ascension Island); in syenite (Serra de Agua de Pau, Azores); in lamproite (Cancarix, Spain). If you start seeing quartz, aegirine, arfvedsonite in float, you are in the right ground. Typical habit: tabular crystals, subhedral grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify dalyite?+
Where is dalyite found?+
What rocks look like dalyite?+
What minerals are found with dalyite?+
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Find dalyite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
