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 — that is 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.
