Bertrandite is a primary ore of beryllium that commonly forms as delicate, tabular to prismatic crystals in cavities. It is frequently found as a secondary mineral replacing beryl in pegmatites or in hydrothermal deposits associated with fluorite and other beryllium minerals. Collectors value it for its sharp, glassy luster and complex crystal formations, though specimens require careful handling due to the toxicity of beryllium.
Is this bertrandite?
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 bertrandite with a known reference. Bertrandite sits at Mohs 6-7, 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, pearly on {001}.
- 4Match the color rangeCompare against the expected color range: colorless, pale yellow.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: crystalline, prismatic, tabular.
Often confused with
Bertrandite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Bertrandite is noticeably harder (Mohs 6-7 vs. 4.5-5).
How to tell apart: Bertrandite is noticeably harder (Mohs 6-7 vs. 3-3.5); luster reads vitreous, pearly on {001} on Bertrandite and adamantine, tending toward vitreous, resinous on Cerussite.
Often found alongside bertrandite
Minerals reported to co-occur with bertrandite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Be₄Si₂O₇(OH)₂
- Mohs hardness
- 6-7
- Density
- 2.59-2.60 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous, pearly on {001}
- Transparency
- Transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Crystalline, prismatic, tabular
- Cleavage
- Perfect on {001}; distinct on {100}, {010}, and {110}
- Rarity
- Uncommon
- Uses
- Collector, Ore of beryllium
- Host rock
- In fissures in granites and associated pegmatites and in miarolitic cavities in greisens; commonly an alteration product of beryl, more rarely as a primary mineral
Where rockhounds find bertrandite
3 mapped spotsClassic worldwide localities
- Strickland quarry, Portland, Middlesex Co., Connecticut, USA
- Amelia, Amelia Co., Virginia, USA
- Mt. Antero, Chaffee Co., Colorado, USA
- Spor Mountain, Juab Co., Utah, a large commercial deposit, USA
- Nantes, in the Barbin quarries at Petit-Port, Loire-Atlantique, France
- Val Vigezzo, Piedmont, Italy
Field-hunting tip
Where it forms: In fissures in granites and associated pegmatites and in miarolitic cavities in greisens; commonly an alteration product of beryl, more rarely as a primary mineral. If you start seeing beryl, phenakite, herderite in float, you are in the right ground. Typical habit: crystalline, prismatic, tabular. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Colorado, Utah, Wisconsin. Start trip planning there.
Common questions
How do you identify bertrandite?+
Where is bertrandite found?+
Can I find bertrandite in the United States?+
Is bertrandite safe to handle?+
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Find bertrandite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
