Gyrolite is a fascinating silicate mineral that typically forms distinct, spherical radiating clusters or globular masses within basalt cavities. It is easily recognized by its characteristic pearly luster and white to pale yellow color. Collectors often prize it for its association with beautiful zeolite minerals like apophyllite and prehnite.
Is this gyrolite?
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 gyrolite with a known reference. Gyrolite 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. Gyrolite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Gyrolite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: white, yellowish, greenish, brownish.
- 5Look at form & habitCrystal system: trigonal. Typical habit: spherical radiating aggregates, globular, bladed crystals.
Often confused with
Gyrolite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Prehnite is the harder of the two (Mohs 6-6.5 vs. 3-4); luster reads pearly on Gyrolite and vitreous on Prehnite.
How to tell apart: Luster reads pearly on Gyrolite and vitreous to pearly on Apophyllite.
Often found alongside gyrolite
Minerals reported to co-occur with gyrolite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCa₁₆Si₂₄O₆₀(OH)₈·14H₂O
- Mohs hardness
- 3-4
- Density
- 2.3-2.4 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Spherical Radiating Aggregates, Globular, Bladed Crystals
- Cleavage
- Perfect Basal
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- Basaltic Vugs and Cavities
- Typical price
- $10-60 for cabinet specimens
Where rockhounds find gyrolite
1 mapped spotsClassic worldwide localities
- Mumbai, India
- Skye, Scotland
- Faroe Islands
- Iceland
- Fairfax Quarry, Virginia, USA
Field-hunting tip
Look in basaltic vugs and cavities country — that is the host setting where gyrolite typically forms. If you start seeing apophyllite, prehnite, calcite in float, you are in the right ground. Field specimens usually show a spherical radiating aggregates, globular, bladed crystals habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in California — start trip planning there.
Common questions
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Find gyrolite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
