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, 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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