Hodgkinsonite is a rare silicate mineral primarily known from the unique zinc ore deposits of the Franklin Mining District. It is highly sought after by fluorescent mineral collectors due to its vivid orange-red reaction under shortwave UV light. Collectors should look for transparent pink to reddish prisms often associated with other rare zinc-manganese minerals.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent to translucent

mineralrare

Hodgkinsonite

Hardness: <5
Luster: Vitreous
Streak: White
Transparency: Transparent to translucent

Is this hodgkinsonite?

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 hodgkinsonite with a known reference. Hodgkinsonite 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. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: light pink, orange, reddish brown.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: acicular, radial.

Often confused with

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

How to tell apart: Luster reads vitreous on Hodgkinsonite and brilliant, glassy; pearly on {010} on Clinohedrite.

How to tell apart: Luster reads vitreous on Hodgkinsonite and dull to slightly greasy on Esperite.

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Often found alongside hodgkinsonite

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

All properties

Chemical formula: Zn₂Mn²⁺(SiO₄)(OH)₂
Mohs hardness: <5
Density: 4.06-4.08 g/cm³
Colors: Light pink Orange Reddish brown
Streak: White
Luster: Vitreous
Transparency: Transparent to translucent
Crystal system: Monoclinic
Crystal habit: Acicular, radial
Cleavage: Perfect on {001}
Fluorescence: Red under LW UV
Rarity: Rare
Uses: Collector
Host rock: As seams in massive willemite-franklinite granular ore in a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA)

Where rockhounds find hodgkinsonite

Classic worldwide localities

Franklin and Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA

Field-hunting tip

Where it forms: As seams in massive willemite-franklinite granular ore in a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA). If you start seeing barite, willemite, franklinite in float, you are in the right ground. Typical habit: acicular, radial. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify hodgkinsonite?+

Mohs hardness is <5. Luster: vitreous. The streak is white. Common colors include light pink, orange, reddish brown.

Where is hodgkinsonite found?+

Notable localities include Franklin and Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA.

Is hodgkinsonite safe to handle?+

Contains zinc and manganese; handle with care and wash hands after handling to avoid ingestion of dust.

What rocks look like hodgkinsonite?+

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

What minerals are found with hodgkinsonite?+

Hodgkinsonite commonly co-occurs with Barite, Willemite, Franklinite, Tephroite, Pyrochroite, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does hodgkinsonite form in?+

Where it forms: As seams in massive willemite-franklinite granular ore in a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA). Working float back to the host body is the standard way to chase a fresh occurrence.

What is hodgkinsonite used for?+

Hodgkinsonite is used in collector.

Find hodgkinsonite on the map

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