Bobierrite is a rare magnesium phosphate mineral typically found in guano deposits where it forms delicate, pearly tabular crystals. It is chemically similar to vivianite but lacks iron, often occurring as white or colorless radiating sprays or crusts associated with other secondary phosphates.
Is this bobierrite?
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 bobierrite with a known reference. Bobierrite sits at Mohs 2-2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: nearly vitreous to pearly on cleavages.
- 4Match the color rangeCompare against the expected color range: colorless, gray, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, radiating aggregates, crusts.
Often confused with
Bobierrite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads nearly vitreous to pearly on cleavages on Bobierrite and vitreous, pearly on the cleavage, dull when earthy on Vivianite.
How to tell apart: Luster reads nearly vitreous to pearly on cleavages on Bobierrite and vitreous on Newberyite.
Often found alongside bobierrite
Minerals reported to co-occur with bobierrite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Mg₃(PO₄)₂·8H₂O
- Mohs hardness
- 2-2.5
- Density
- 2.195 g/cm³
- Streak
- White
- Luster
- Nearly vitreous to pearly on cleavages
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals, radiating aggregates, crusts
- Cleavage
- {010}, perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Formed from the chemical alteration of guano deposits (Mejillones, Chile; Imperial Canyon lava tubes, Kenya), and an elephant tusk (Edgerton, Minnesota, USA)
Where rockhounds find bobierrite
Classic worldwide localities
- Found near Edgerton, Pipestone Co., Minnesota, USA
- Found on Mejillones Island, Chile
- Western Australia, found in the Pilbara district, at Wodgina
- Marlborough, New Zealand
- Bendada pegmatite, near Guarda, Portugal
- Zheleznyi iron mine, Kovdor massif, Kola Peninsula, Russia
Field-hunting tip
Where it forms: Formed from the chemical alteration of guano deposits (Mejillones, Chile; Imperial Canyon lava tubes, Kenya), and an elephant tusk (Edgerton, Minnesota, USA). If you start seeing hannayite, schertelite, lithiophilite in float, you are in the right ground. Typical habit: tabular crystals, radiating aggregates, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify bobierrite?+
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What rocks look like bobierrite?+
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Find bobierrite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
