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, 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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