Johnbaumite is an uncommon arsenate member of the apatite group named in honor of mineralogist John L. Baum. It typically occurs as small, pale prismatic crystals in metamorphic zinc deposits, most famously associated with the Franklin, New Jersey ore bodies.
Is this johnbaumite?
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 johnbaumite with a known reference. Johnbaumite sits at Mohs ~4.5, 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: adamantine to greasy on fracture surfaces, vitreous on cleavage surfaces.
- 4Match the color rangeCompare against the expected color range: white, colorless.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: anhedral grains, massive.
Often confused with
Johnbaumite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads adamantine to greasy on fracture surfaces, vitreous on cleavage surfaces on Johnbaumite and vitreous on Apatite.
How to tell apart: Luster reads adamantine to greasy on fracture surfaces, vitreous on cleavage surfaces on Johnbaumite and resinous to subadamantine on Mimetite.
Often found alongside johnbaumite
Minerals reported to co-occur with johnbaumite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₅(AsO₄)₃OH
- Mohs hardness
- ~4.5
- Density
- 3.68 g/cm³
- Streak
- White
- Luster
- Adamantine to greasy on fracture surfaces, vitreous on cleavage surfaces
- Transparency
- Translucent
- Crystal system
- Hexagonal
- Crystal habit
- Anhedral grains, massive
- Cleavage
- Distinct on {1010}
- Fluorescence
- Pink orange under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A very rare mineral, part of a metamorphic skarn assemblage in a metamorphosed stratiform zinc orebody (Franklin, New Jersey, USA)
Where rockhounds find johnbaumite
Classic worldwide localities
- Franklin and Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA
- Novofrolovskoye copper deposit, Turinsk district, near Krasnoturinsk, Northern Ural Mountains and Yuliya Svintsovaya Pb-Zn deposit, 20 km east-northeast of Son railway station, western Siberia, Russia
- Harstigen mine, Långban, Värmland, Sweden
- Fuka mine, Okayama Prefecture, Japan
Field-hunting tip
Where it forms: A very rare mineral, part of a metamorphic skarn assemblage in a metamorphosed stratiform zinc orebody (Franklin, New Jersey, USA). If you start seeing yeatmanite, diopside, andradite in float, you are in the right ground. Typical habit: anhedral grains, massive. Train your eye for that shape before scanning the outcrop.
Common questions
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Find johnbaumite on the map
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