Bobcookite is an extremely rare beryllium-bearing mineral known primarily from the alkaline complex at Mount Saint-Hilaire. It typically forms delicate, colorless to white needle-like crystals or fibrous crusts associated with other late-stage pegmatitic minerals. Collectors should look for it in small cavities within nepheline syenite xenoliths.
Is this bobcookite?
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 bobcookite with a known reference. Bobcookite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Bobcookite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Bobcookite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular to fibrous sprays or crusts.
Often found alongside bobcookite
Minerals reported to co-occur with bobcookite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaAlBeSi₂O₆·4H₂O
- Mohs hardness
- 2
- Density
- 2.44 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular to Fibrous Sprays or Crusts
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Alkaline Igneous Intrusions
- Typical price
- $50-300 per specimen
Where rockhounds find bobcookite
Classic worldwide localities
- Mount Saint-Hilaire, Quebec, Canada
Field-hunting tip
Look in alkaline igneous intrusions country — that is the host setting where bobcookite typically forms. If you start seeing sodalite, analcime, natrolite in float, you are in the right ground. Field specimens usually show a acicular to fibrous sprays or crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find bobcookite on the map
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