Hyalite is a transparent, colorless variety of opal that typically forms botryoidal crusts or glassy, globular aggregates. It is most famous among collectors for its spectacular, intense neon-green fluorescence caused by uranyl ion inclusions, making it a favorite for display under UV lighting.
Is this hyalite opal?
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 hyalite opal with a known reference. Hyalite Opal sits at Mohs 5.5-6.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Hyalite Opal leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Hyalite Opal typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, yellowish.
- 5Look at form & habitCrystal system: amorphous. Typical habit: botryoidal, crusts, globular, stalactitic.
Often confused with
Hyalite Opal vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside hyalite opal
Minerals reported to co-occur with hyalite opal. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂·nH₂O
- Mohs hardness
- 5.5-6.5
- Density
- 2.0-2.2 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Amorphous
- Crystal habit
- Botryoidal, Crusts, Globular, Stalactitic
- Cleavage
- None
- Fluorescence
- Intense Bright Green Under SW and LW UV
- Rarity
- Uncommon
- Uses
- Collector, Lapidary
- Host rock
- Volcanic Cavities, Hydrothermal Veins
- Typical price
- $10-100 thumbnail, $50-500 cabinet specimen
Where rockhounds find hyalite opal
7 mapped spotsClassic worldwide localities
- Mexico
- Czech Republic
- USA
- Hungary
- Germany
Field-hunting tip
Look in volcanic cavities, hydrothermal veins country — that is the host setting where hyalite opal typically forms. If you start seeing quartz, calcite, zeolites in float, you are in the right ground. Field specimens usually show a botryoidal, crusts, globular, stalactitic habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in North Carolina, Maryland, Montana — start trip planning there.
Common questions
How do you identify hyalite opal?+
Where is hyalite opal found?+
Can I find hyalite opal in the United States?+
How much is hyalite opal worth?+
What rocks look like hyalite opal?+
What minerals are found with hyalite opal?+
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Find hyalite opal on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
