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, so 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, 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.