Bobshannonite is a very rare member of the lomonosovite group, typically identified by its distinct brownish-red tabular crystal morphology. It is primarily known from the alkaline complex at Mont Saint-Hilaire, where it occurs within pegmatitic miarolitic cavities alongside a suite of complex titanium and silicate minerals.
Is this bobshannonite?
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 bobshannonite with a known reference. Bobshannonite sits at Mohs ~4, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: very pale brown.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to frosted.
- 4Match the color rangeCompare against the expected color range: orange-brown.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy crystals.
Often confused with
Bobshannonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Bobshannonite leaves very pale brown, Lomonosovite leaves light rose-cinnamon.
How to tell apart: Bobshannonite is noticeably harder (Mohs ~4 vs. 2-3); streak differs, so Bobshannonite leaves very pale brown, Murmanite leaves white.
Often found alongside bobshannonite
Minerals reported to co-occur with bobshannonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂KBa(Mn,Na)₈(Nb,Ti)₄(Si₂O₇)₄O₄(OH)₄(O,F)₂
- Mohs hardness
- ~4
- Density
- 3.787 g/cm³
- Colors
- Streak
- Very pale brown
- Luster
- Vitreous to frosted
- Transparency
- Transparent to translucent
- Crystal system
- Triclinic
- Crystal habit
- Platy crystals
- Cleavage
- Very good on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A hydrothermal phase in a pegmatite associated with an intrusive alkaline gabbro-syenite complex
Where rockhounds find bobshannonite
Classic worldwide localities
- Poudrette quarry, Mont Saint-Hilaire, La Vallée-du-Richelieu RCM, Monterégie, Québec, Canada
Field-hunting tip
Where it forms: A hydrothermal phase in a pegmatite associated with an intrusive alkaline gabbro-syenite complex. If you start seeing sérandite, albite, aegirine in float, you are in the right ground. Typical habit: platy crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find bobshannonite on the map
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