Esperite is a rare lead-calcium silicate mineral famous for its brilliant yellow-green fluorescence under shortwave UV light. It is primarily found in the metamorphosed ore deposits of Franklin and Sterling Hill, New Jersey, where it often occurs in massive or granular form alongside willemite.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

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Esperite

Also: Calcium-larsenite

Hardness: 5
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this esperite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch esperite with a known reference. Esperite sits at Mohs 5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Esperite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Esperite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: white, yellow, colorless.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: massive, granular, or prismatic.

Often confused with

Esperite vs. its common look-alikes — and how to tell them apart in the field.

How to tell apart: Esperite is noticeably harder (Mohs 5 vs. 3).

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Often found alongside esperite

Minerals reported to co-occur with esperite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: PbCa₃(ZnSiO₄)₄
Mohs hardness: 5
Density: 3.37 g/cm³
Colors: White Yellow Colorless
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Massive, Granular, Or Prismatic
Cleavage: Distinct On {100}
Fluorescence: Bright Yellow-green Under SW UV
Rarity: Rare
Uses: Collector, Fluorescent Specimen
Host rock: Metamorphosed Zinc Ore Deposits
Typical price: $20-200 depending on specimen size and fluorescence quality

Where rockhounds find esperite

Classic worldwide localities

Franklin, New Jersey, USA
Sterling Hill, New Jersey, USA

Field-hunting tip

Look in metamorphosed zinc ore deposits country — that is the host setting where esperite typically forms. If you start seeing willemite, franklinite, zincite in float, you are in the right ground. Field specimens usually show a massive, granular, or prismatic habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify esperite?+

Mohs hardness is 5. It typically shows a vitreous luster. The streak is white. Common colors include white, yellow, colorless.

Where is esperite found?+

Notable localities include Franklin, New Jersey, USA; Sterling Hill, New Jersey, USA.

How much is esperite worth?+

Typical asking prices fall in the range of $20-200 depending on specimen size and fluorescence quality. Quality, size, and provenance can move individual specimens well outside that range.

Is esperite safe to handle?+

It contains toxic constituents. Contains lead and zinc; wash hands thoroughly after handling and avoid inhaling dust when cleaning specimens. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like esperite?+

Esperite is most often confused with Willemite, Hardystonite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with esperite?+

Esperite commonly co-occurs with Willemite, Franklinite, Zincite, Hardystonite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does esperite form in?+

Esperite typically forms in metamorphosed zinc ore deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is esperite used for?+

Esperite is used in collector, fluorescent specimen.

Find esperite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.