Eudidymite is a rare beryllium silicate that often forms distinct pseudo-hexagonal, tabular crystals. It is chemically dimorphous with epididymite and is primarily found as a late-stage mineral in alkaline pegmatites, frequently appearing as white, bladed aggregates.
Is this eudidymite?
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 eudidymite with a known reference. Eudidymite sits at Mohs 5.5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Eudidymite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Eudidymite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular, pseudo-hexagonal crystals, often in radiating sprays or as coatings.
Often confused with
Eudidymite vs. its common look-alikes, and how to tell them apart in the field.
Often found alongside eudidymite
Minerals reported to co-occur with eudidymite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaBeSi₃O₈(OH)
- Mohs hardness
- 5.5-6
- Density
- 2.55 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular, Pseudo-hexagonal Crystals, Often in Radiating Sprays or as Coatings
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Rocks, Pegmatites
- Typical price
- $20-150 thumbnail
Where rockhounds find eudidymite
Classic worldwide localities
- Langesundsfjord, Norway
- Kola Peninsula, Russia
- Mont Saint-Hilaire, Canada
Field-hunting tip
Look in alkaline igneous rocks, pegmatites country, the host setting where eudidymite typically forms. If you start seeing epididymite, aegirine, microcline in float, you are in the right ground. Field specimens usually show a tabular, pseudo-hexagonal crystals, often in radiating sprays or as coatings habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify eudidymite?+
Where is eudidymite found?+
How much is eudidymite worth?+
What rocks look like eudidymite?+
What minerals are found with eudidymite?+
What kind of rock does eudidymite form in?+
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Find eudidymite on the map
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