Eskolaite is a rare chromium oxide mineral known for its distinct deep emerald green color and high hardness. It is typically found as small, opaque crystals within metamorphic rocks like skarns or as granular masses associated with other chromium-bearing minerals.
Is this eskolaite?
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 eskolaite with a known reference. Eskolaite sits at Mohs 8.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Eskolaite leaves a light green streak.
- 3Read the lusterHold the specimen under a strong light. Eskolaite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: emerald green, dark green, blackish green.
- 5Look at form & habitCrystal system: trigonal. Typical habit: tabular crystals, massive, granular.
Often confused with
Eskolaite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Eskolaite is noticeably harder (Mohs 8.5 vs. 5-6.5); streak differs — Eskolaite leaves light green, Iron Ore leaves reddish-brown to black; luster reads metallic on Eskolaite and metallic to submetallic on Iron Ore.
How to tell apart: Eskolaite is noticeably harder (Mohs 8.5 vs. 5-6); streak differs — Eskolaite leaves light green, Manaccanite leaves black; luster reads metallic on Eskolaite and submetallic on Manaccanite.
How to tell apart: Streak differs — Eskolaite leaves light green, Corundum leaves white; luster reads metallic on Eskolaite and vitreous on Corundum.
Often found alongside eskolaite
Minerals reported to co-occur with eskolaite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cr₂O₃
- Mohs hardness
- 8.5
- Density
- 5.21 g/cm³
- Streak
- Light Green
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Tabular Crystals, Massive, Granular
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific Research
- Host rock
- Metamorphic Rocks, Specifically Chromium-rich Skarns and Serpentinites
- Typical price
- $100-500+ for specimen quality
Where rockhounds find eskolaite
Classic worldwide localities
- Outokumpu, Finland
- Kola Peninsula, Russia
- Harts Range, Australia
- California, USA
Field-hunting tip
Look in metamorphic rocks, specifically chromium-rich skarns and serpentinites country — that is the host setting where eskolaite typically forms. If you start seeing uvarovite, chromite, tremolite in float, you are in the right ground. Field specimens usually show a tabular crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find eskolaite on the map
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