Glauconite is a characteristic green mica mineral typically found as dull, granular pellets in marine sedimentary rocks. It is highly valued by geologists as an indicator of slow depositional rates in shallow marine environments and is commonly associated with sandstones and limestones.
Is this glauconite?
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 glauconite with a known reference. Glauconite sits at Mohs 2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Glauconite leaves a pale green streak.
- 3Read the lusterHold the specimen under a strong light. Glauconite typically shows a dull luster.
- 4Match the color rangeCompare against the expected color range: green, olive-green, yellowish-green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: earthy, granular, or pellet-like masses.
Often confused with
Glauconite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Glauconite leaves pale green, Celadonite leaves white.
How to tell apart: Streak differs — Glauconite leaves pale green, Chlorite leaves white; luster reads dull on Glauconite and pearly on Chlorite.
Often found alongside glauconite
Minerals reported to co-occur with glauconite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (K,Na)(Fe³⁺,Al,Mg)₂(Si,Al)₄O₁₀(OH)₂
- Mohs hardness
- 2
- Density
- 2.4-2.95 g/cm³
- Streak
- Pale Green
- Luster
- Dull
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Earthy, Granular, Or Pellet-like Masses
- Cleavage
- Perfect Basal
- Rarity
- Common
- Uses
- Geological Indicator, Soil Additive
- Host rock
- Sedimentary Marine Environments
- Typical price
- $5-20 for bulk mineral specimens
Where rockhounds find glauconite
2 mapped spotsClassic worldwide localities
- New Jersey, USA
- England
- Belgium
- France
- Russia
Field-hunting tip
Look in sedimentary marine environments country — that is the host setting where glauconite typically forms. If you start seeing calcite, quartz, goethite in float, you are in the right ground. Field specimens usually show a earthy, granular, or pellet-like masses habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Missouri, Utah — start trip planning there.
Common questions
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Find glauconite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
