Roeblingite is a rare lead-calcium silicate mineral primarily known from the unique zinc mines of Franklin and Sterling Hill, New Jersey. It is most easily identified by its striking bright yellow to orange fluorescence under shortwave UV light. Collectors typically find it in massive form associated with other fluorescent minerals like willemite.
Is this roeblingite?
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 roeblingite with a known reference. Roeblingite sits at Mohs <3, 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: dull to somewhat resinous.
- 4Match the color rangeCompare against the expected color range: white, pink.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive.
Often confused with
Roeblingite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Luster reads dull to somewhat resinous on Roeblingite and vitreous on Hardystonite.
How to tell apart: Willemite is the harder of the two (Mohs 5.5 vs. <3); luster reads dull to somewhat resinous on Roeblingite and vitreous to resinous on Willemite.
Often found alongside roeblingite
Minerals reported to co-occur with roeblingite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₂Ca₆Mn(Si₃O₉)₂(SO₄)₂(OH)₂(H₂O)₄
- Mohs hardness
- <3
- Density
- 3.433 g/cm³
- Streak
- White
- Luster
- Dull to somewhat resinous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Massive
- Cleavage
- Perfect on {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As nodular masses in calcium silicate lenses containing abundant garnet (Franklin, New Jersey, USA); as fracture fillings in a metamorphosed Fe{Mn orebody (Långban, Sweden)
Where rockhounds find roeblingite
Classic worldwide localities
- Franklin, Sussex Co., New Jersey, USA
- Långban, Värmland, Sweden
Field-hunting tip
Where it forms: As nodular masses in calcium silicate lenses containing abundant garnet (Franklin, New Jersey, USA); as fracture fillings in a metamorphosed Fe{Mn orebody (Långban, Sweden). If you start seeing garnet, titanite, zircon in float, you are in the right ground. Typical habit: massive. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify roeblingite?+
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Is roeblingite safe to handle?+
What rocks look like roeblingite?+
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Find roeblingite on the map
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