Mcgovernite is a rare manganese zinc arsenate-silicate mineral known primarily from the unique ore deposits of Franklin and Sterling Hill, New Jersey. It typically occurs as bronze-colored foliated or tabular crystals associated with other rare zinc minerals.

Hardness

Mohs

Luster

Pearly

Streak

Brown

Transparency

Semitransparent

mineralrare

Mcgovernite

Hardness: 3
Luster: Pearly
Streak: Brown
Transparency: Semitransparent

Is this mcgovernite?

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 mcgovernite with a known reference. Mcgovernite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: brown.
3
Read the luster
Hold the specimen under a strong light. Luster: pearly.
4
Match the color range
Compare against the expected color range: bronze brown, light brown, dark reddish brown, reddish brown.
5
Look at form & habit
Crystal system: trigonal. Typical habit: massive, micaceous.

Often confused with

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

mineral

Friedelite

Mohs 4-5

How to tell apart: Friedelite is the harder of the two (Mohs 4-5 vs. 3); streak differs, so Mcgovernite leaves brown, Friedelite leaves pale rose; luster reads pearly on Mcgovernite and vitreous, pearly on basal plane on Friedelite.

How to tell apart: Streak differs, so Mcgovernite leaves brown, Dixenite leaves brownish-red; luster reads pearly on Mcgovernite and metallic to resinous on Dixenite.

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Often found alongside mcgovernite

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

All properties

Chemical formula: Zn₃(Mn,Mg,Fe,Al)₄₂(AsO₃)₂(AsO₄)₄[(Si,As)O₄]₈(OH)₄₂
Mohs hardness: 3
Density: 3.719 g/cm³
Colors: Bronze brown Light brown Dark reddish brown Reddish brown
Streak: Brown
Luster: Pearly
Transparency: Semitransparent
Crystal system: Trigonal
Crystal habit: Massive, micaceous
Cleavage: Perfect micaceous on {0001}
Rarity: Rare
Uses: Collector
Host rock: As the principal filling of a vein in massive zinc ore in a metamorphosed stratiform Zn-Mn deposit

Where rockhounds find mcgovernite

Classic worldwide localities

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

Field-hunting tip

Where it forms: As the principal filling of a vein in massive zinc ore in a metamorphosed stratiform Zn-Mn deposit. If you start seeing franklinite, willemite, zincite in float, you are in the right ground. Typical habit: massive, micaceous. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify mcgovernite?+

Mohs hardness is 3. Luster: pearly. The streak is brown. Common colors include bronze brown, light brown, dark reddish brown, reddish brown.

Where is mcgovernite found?+

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

Is mcgovernite safe to handle?+

Mcgovernite contains arsenic and calls for real care. Contains arsenic, which is toxic; wash hands thoroughly after handling specimens and avoid inhaling dust.

What rocks look like mcgovernite?+

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

What minerals are found with mcgovernite?+

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

What kind of rock does mcgovernite form in?+

Where it forms: As the principal filling of a vein in massive zinc ore in a metamorphosed stratiform Zn-Mn deposit. Working float back to the host body is the standard way to chase a fresh occurrence.

What is mcgovernite used for?+

Mcgovernite is used in collector.

Find mcgovernite on the map

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