Nasonite is a rare lead-calcium silicate mineral primarily known from the unique metamorphic deposits of Franklin, New Jersey. It is most easily identified by its distinct, bright blue fluorescence under longwave ultraviolet light, often appearing in massive or granular form associated with other fluorescent minerals like willemite.
Is this nasonite?
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 nasonite with a known reference. Nasonite sits at Mohs 4 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Nasonite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Nasonite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: colorless, white, yellowish, gray.
- 5Look at form & habitCrystal system: hexagonal. Typical habit: granular, massive, rarely in thin tabular crystals.
Often confused with
Nasonite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Nasonite is noticeably harder (Mohs 4 vs. 3).
How to tell apart: Willemite is the harder of the two (Mohs 5.5 vs. 4).
How to tell apart: Clinohedrite is the harder of the two (Mohs 5 vs. 4).
Often found alongside nasonite
Minerals reported to co-occur with nasonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₆Ca₄Si₆O₁₈(Si₂O₇)Cl₂
- Mohs hardness
- 4
- Density
- 5.37 g/cm³
- Streak
- White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Hexagonal
- Crystal habit
- Granular, Massive, Rarely in Thin Tabular Crystals
- Cleavage
- Distinct On {0001}
- Fluorescence
- Bright Blue Under LW UV
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Metamorphosed Zinc-iron-manganese Orebodies
- Typical price
- $50-300 per specimen depending on size and quality
Where rockhounds find nasonite
Classic worldwide localities
- Franklin, New Jersey, USA
- Långban, Sweden
Field-hunting tip
Look in metamorphosed zinc-iron-manganese orebodies country — that is the host setting where nasonite typically forms. If you start seeing willemite, hardystonite, andradite in float, you are in the right ground. Field specimens usually show a granular, massive, rarely in thin tabular crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find nasonite on the map
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