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 — that is 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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