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.
Is this coccolite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry 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.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Coccolite leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Coccolite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: light green, grass green, white.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: granular.
Often confused with
Coccolite vs. its common look-alikes, and how to tell them apart in the field.
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
- 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
- Typical price
- $5-30 for small samples
Where rockhounds find coccolite
1 mapped spotsClassic worldwide localities
- New York, USA
- Finland
- Italy
- Canada
Field-hunting tip
Look in metamorphosed limestone country, the host setting where coccolite typically forms. If you start seeing calcite, phlogopite, scapolite in float, you are in the right ground. Field specimens usually show a granular habit, so 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.
Common questions
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Find coccolite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
