Margarosanite is a rare lead-calcium silicate best known to collectors for its intense and distinctive bright white-to-blue fluorescence under shortwave ultraviolet light. It typically occurs as white, pearly platy crystals or massive granular aggregates in metamorphic environments, most notably the famous zinc mines of Franklin, New Jersey, and the mines at Långban, Sweden.
Is this margarosanite?
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 margarosanite with a known reference. Margarosanite sits at Mohs 2.5-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Margarosanite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Margarosanite typically shows a pearly luster.
- 4Match the color rangeCompare against the expected color range: white, colorless, pale blue.
- 5Look at form & habitCrystal system: triclinic. Typical habit: platy crystals, granular, massive.
Often confused with
Margarosanite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Wollastonite is the harder of the two (Mohs 4.5-5 vs. 2.5-3); luster reads pearly on Margarosanite and vitreous on Wollastonite.
How to tell apart: Pectolite is the harder of the two (Mohs 4.5-5 vs. 2.5-3); luster reads pearly on Margarosanite and vitreous to silky on Pectolite.
Often found alongside margarosanite
Minerals reported to co-occur with margarosanite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb(Ca,Mn)₂Si₃O₉
- Mohs hardness
- 2.5-3
- Density
- 3.99 g/cm³
- Streak
- White
- Luster
- Pearly
- Transparency
- Transparent
- Crystal system
- Triclinic
- Crystal habit
- Platy Crystals, Granular, Massive
- Cleavage
- Perfect in One Direction
- Fluorescence
- Bright White/blue Under SW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Limestone
- Typical price
- $50-500 thumbnail to small cabinet
Where rockhounds find margarosanite
Classic worldwide localities
- Långban, Sweden
- Franklin, New Jersey, USA
- Sterling Hill, New Jersey, USA
Field-hunting tip
Look in metamorphosed limestone country — that is the host setting where margarosanite typically forms. If you start seeing willemite, hardystonite, andradite in float, you are in the right ground. Field specimens usually show a platy crystals, granular, massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify margarosanite?+
Where is margarosanite found?+
How much is margarosanite worth?+
Is margarosanite safe to handle?+
What rocks look like margarosanite?+
What minerals are found with margarosanite?+
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Find margarosanite on the map
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