Greenalite is an iron-rich silicate mineral typically found in sedimentary iron formations and low-grade metamorphic rocks. It rarely forms distinct crystals, usually appearing as fine-grained, earthy, or granular aggregates that can be challenging to distinguish from other iron-bearing phyllosilicates without X-ray diffraction.
Is this greenalite?
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 greenalite with a known reference. Greenalite sits at Mohs 2.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: greenish gray.
- 3Read the lusterHold the specimen under a strong light. Luster: earthy.
- 4Match the color rangeCompare against the expected color range: blue green, light yellow green, dark green, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: microscopic crystals, oolitic.
Often confused with
Greenalite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Greenalite leaves greenish gray, Chamosite leaves green to gray; luster reads earthy on Greenalite and pearly on Chamosite.
How to tell apart: Streak differs, so Greenalite leaves greenish gray, Glauconite leaves light green; luster reads earthy on Greenalite and dull, glistening on Glauconite.
How to tell apart: Cronstedtite is the harder of the two (Mohs 3.5 vs. 2.5); streak differs, so Greenalite leaves greenish gray, Cronstedtite leaves dark olive-green; luster reads earthy on Greenalite and brilliant on Cronstedtite.
Often found alongside greenalite
Minerals reported to co-occur with greenalite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Fe²⁺,Fe³⁺)₂₋₃Si₂O₅(OH)₄
- Mohs hardness
- 2.5
- Density
- 2.85-3.15 g/cm³
- Colors
- Streak
- Greenish gray
- Luster
- Earthy
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Microscopic crystals, oolitic
- Cleavage
- None
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- A primary phase in some banded iron formations
Where rockhounds find greenalite
3 mapped spotsClassic worldwide localities
- Sokoman Iron Formation, Howells River area, Labrador, Newfoundland, Canada
- Gunflint Iron Formation, northeast of Gunflint Lake, Ontario, Canada
- Bluebell mine, Riondel, British Columbia, Canada
- Matsumo mine, Kochi prefecture, Japan
- Weld Range, northwest of Cue, Western Australia
- Salsigne mine, 15 km north of Carcassone, Aude, France
Field-hunting tip
Where it forms: A primary phase in some banded iron formations. If you start seeing minnesotaite, stilpnomelane, siderite in float, you are in the right ground. Typical habit: microscopic crystals, oolitic. Train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Minnesota. Start trip planning there.
Common questions
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Find greenalite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
