Kellyite is a rare manganese-rich member of the serpentine group. It typically appears as yellowish-green micaceous or platy aggregates found within metamorphic manganese ore bodies.

Hardness

2.5

Mohs

Luster

Pearly

Streak

White

Transparency

Translucent

mineralrareSerpentine Group family

Kellyite

Kellyite is a rare manganese-rich member of the serpentine group. It typically appears as yellowish-green micaceous or platy aggregates found within metamorphic manganese ore bodies.

Hardness: 2.5
Luster: Pearly
Streak: White
Transparency: Translucent

Is this kellyite?

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 kellyite with a known reference. Kellyite sits at Mohs 2.5 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Kellyite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Kellyite typically shows a pearly luster.
4
Match the color range
Compare against the expected color range: yellow, yellow-green.
5
Look at form & habit
Crystal system: trigonal. Typical habit: platy crystals, micaceous masses.

Often confused with

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

mineral

Chamosite

Mohs 3

How to tell apart: Streak differs — Kellyite leaves white, Chamosite leaves white to pale green.

Often found alongside kellyite

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

All properties

Chemical formula: (Mn²⁺,Mg,Al)₆(Si,Al)₄O₁₀(OH)₈
Mohs hardness: 2.5
Density: 2.8 g/cm³
Colors: Yellow Yellow-green
Streak: White
Luster: Pearly
Transparency: Translucent
Crystal system: Trigonal
Crystal habit: Platy Crystals, Micaceous Masses
Cleavage: Perfect Basal
Rarity: Rare
Uses: Collector
Host rock: Metamorphosed Manganese Deposits
Typical price: $50-300 per specimen

Where rockhounds find kellyite

Classic worldwide localities

Bald Knob, North Carolina, USA
Franklin, New Jersey, USA

Field-hunting tip

Look in metamorphosed manganese deposits country — that is the host setting where kellyite typically forms. If you start seeing alleghanyite, gahnite, hausmannite in float, you are in the right ground. Field specimens usually show a platy crystals, micaceous masses habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify kellyite?+

Mohs hardness is 2.5. It typically shows a pearly luster. The streak is white. Common colors include yellow, yellow-green.

Where is kellyite found?+

Notable localities include Bald Knob, North Carolina, USA; Franklin, New Jersey, USA.

How much is kellyite worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like kellyite?+

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

What minerals are found with kellyite?+

Kellyite commonly co-occurs with Alleghanyite, Gahnite, Hausmannite, Jacobsite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does kellyite form in?+

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

What is kellyite used for?+

Kellyite is used in collector.

Find kellyite on the map

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