Nelenite is a rare manganese silicate mineral primarily known from the unique zinc mines of Franklin and Sterling Hill. It typically appears as yellowish-brown tabular crystals or foliated masses often associated with willemite and franklinite.

Hardness

Mohs

Luster

Vitreous on cleavages, resinous and duller on fractures

Streak

Light brown

Transparency

Transparent

mineralrareFriedelite Group family

Nelenite

Hardness: ~5
Luster: Vitreous on cleavages, resinous and duller on fractures
Streak: Light brown
Transparency: Transparent

Is this nelenite?

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 nelenite with a known reference. Nelenite 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: light brown.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous on cleavages, resinous and duller on fractures.
4
Match the color range
Compare against the expected color range: brown.
5
Look at form & habit
Crystal system: trigonal. Typical habit: crystalline, massive.

Often confused with

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

mineral

Friedelite

Mohs 4-5

How to tell apart: Streak differs, so Nelenite leaves light brown, Friedelite leaves pale rose.

Compare →

Often found alongside nelenite

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

All properties

Chemical formula: Mn₁₆As₃Si₁₂O₃₆(OH)₁₇
Mohs hardness: ~5
Density: 3.46 g/cm³
Colors: Brown
Streak: Light brown
Luster: Vitreous on cleavages, resinous and duller on fractures
Transparency: Transparent
Crystal system: Trigonal
Crystal habit: Crystalline, massive
Cleavage: {0001}, perfect
Rarity: Rare
Uses: Collector
Host rock: In a metamorphosed stratiform zinc deposit, within pegmatitic textured masses, and as calcite-cemented fragments in a breccia probably derived from the pegmatitic material

Where rockhounds find nelenite

Classic worldwide localities

Franklin, Sussex Co., New Jersey, USA

Field-hunting tip

Where it forms: In a metamorphosed stratiform zinc deposit, within pegmatitic textured masses, and as calcite-cemented fragments in a breccia probably derived from the pegmatitic material. If you start seeing actinolite, calcite, willemite in float, you are in the right ground. Typical habit: crystalline, massive. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify nelenite?+

Mohs hardness is ~5. Luster: vitreous on cleavages, resinous and duller on fractures. The streak is light brown. Common colors include brown.

Where is nelenite found?+

Notable localities include Franklin, Sussex Co., New Jersey, USA.

Is nelenite safe to handle?+

Nelenite contains arsenic and calls for real care. Contains manganese and potentially other heavy metals; handle with care to avoid ingestion or inhalation of dust.

What rocks look like nelenite?+

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

What minerals are found with nelenite?+

Nelenite commonly co-occurs with Actinolite, Calcite, Willemite, Tirodite, Rhodonite, Apatite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does nelenite form in?+

Where it forms: In a metamorphosed stratiform zinc deposit, within pegmatitic textured masses, and as calcite-cemented fragments in a breccia probably derived from the pegmatitic material. Working float back to the host body is the standard way to chase a fresh occurrence.

What is nelenite used for?+

Nelenite is used in collector.

Find nelenite on the map

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