Ferrobobfergusonite is a rare phosphate mineral found primarily within complex granite pegmatites. It typically occurs as part of a mineral series where iron replaces manganese, making it structurally related to the bobfergusonite-group species found in the Black Hills of South Dakota.
Is this ferrobobfergusonite?
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 ferrobobfergusonite with a known reference. Ferrobobfergusonite sits at Mohs 4.5-5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Ferrobobfergusonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Ferrobobfergusonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: brown, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: granular to prismatic crystals.
Often confused with
Ferrobobfergusonite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside ferrobobfergusonite
Minerals reported to co-occur with ferrobobfergusonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Na₂Fe²⁺₅Fe³⁺Al(PO₄)₆
- Mohs hardness
- 4.5-5
- Density
- 3.58 g/cm³
- Colors
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Granular to Prismatic Crystals
- Cleavage
- Distinct On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Granite Pegmatites
- Typical price
- $50-300 per specimen
Where rockhounds find ferrobobfergusonite
Classic worldwide localities
- Tip Top Mine, South Dakota, USA
- Bull Moose Mine, South Dakota, USA
Field-hunting tip
Look in granite pegmatites country — that is the host setting where ferrobobfergusonite typically forms. If you start seeing quartz, albite, muscovite in float, you are in the right ground. Field specimens usually show a granular to prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferrobobfergusonite?+
Where is ferrobobfergusonite found?+
How much is ferrobobfergusonite worth?+
What rocks look like ferrobobfergusonite?+
What minerals are found with ferrobobfergusonite?+
What kind of rock does ferrobobfergusonite form in?+
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Find ferrobobfergusonite on the map
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