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. Roeblingite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Roeblingite typically shows a dull to resinous luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pale pink.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: massive, granular, or fine-grained aggregates.
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 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 resinous on Roeblingite and vitreous 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
- Pb₂Ca₆(Si₃O₉)₂(SO₄)(OH)₂·4H₂O
- Mohs hardness
- 3
- Density
- 3.433 g/cm³
- Streak
- White
- Luster
- Dull to Resinous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Massive, Granular, Or Fine-grained Aggregates
- Cleavage
- Perfect On 001
- Fluorescence
- Bright Yellow to Orange Under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Zinc Ore Deposits
Where rockhounds find roeblingite
Classic worldwide localities
- Franklin, New Jersey, USA
- Sterling Hill, New Jersey, USA
Field-hunting tip
Look in metamorphosed zinc ore deposits country, the host setting where roeblingite typically forms. If you start seeing willemite, hardystonite, ganophyllite in float, you are in the right ground. Field specimens usually show a massive, granular, or fine-grained aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find roeblingite on the map
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