Coccolite is a granular or friable variety of diopside often found in metamorphosed limestone or marble deposits. It is easily identified by its light green, granular appearance and its occurrence within calc-silicate contact metamorphic rocks.

Hardness

5.5-6.5

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralcommonDiopside family

Coccolite

Also: granular diopside

Hardness: 5.5-6.5
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this coccolite?

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 coccolite with a known reference. Coccolite sits at Mohs 5.5-6.5, 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 green, grass green, white.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: granular.

Often confused with

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

mineral

Augite

Mohs 5.5-6

How to tell apart: Streak differs, so Coccolite leaves white, Augite leaves gray-green.

How to tell apart: Streak differs, so Coccolite leaves white, Epidote leaves grayish white.

Compare →

Often found alongside coccolite

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

All properties

Chemical formula: CaMgSi₂O₆
Mohs hardness: 5.5-6.5
Density: 3.2-3.3 g/cm³
Colors: Light green Grass green White
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Granular
Cleavage: Good in two directions
Rarity: Common
Uses: Collector, Geological study
Host rock: metamorphosed limestone

Where rockhounds find coccolite

1 mapped spots

Classic worldwide localities

New York, USA
Finland
Italy
Canada

Field-hunting tip

Where it forms: metamorphosed limestone. If you start seeing calcite, phlogopite, scapolite in float, you are in the right ground. Typical habit: granular. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New Jersey. Start trip planning there.

Browse 1 U.S. spots for coccolite →

More coccolite photos

Common questions

How do you identify coccolite?+

Mohs hardness is 5.5-6.5. Luster: vitreous. The streak is white. Common colors include light green, grass green, white.

Where is coccolite found?+

Notable localities include New York, USA; Finland; Italy; Canada.

Can I find coccolite in the United States?+

RockHoundR maps 1 coccolite rockhounding spots across 1 U.S. states. The top states are New Jersey.

What rocks look like coccolite?+

Coccolite is most often confused with Augite, Tremolite, Epidote. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with coccolite?+

Coccolite commonly co-occurs with calcite, phlogopite, scapolite, titanite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does coccolite form in?+

Where it forms: metamorphosed limestone. Working float back to the host body is the standard way to chase a fresh occurrence.

What is coccolite used for?+

Coccolite is used in collector, geological study.

Find coccolite on the map

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