Erdite is a very rare sodium iron sulfide mineral often found as thin, platy crystals or delicate crusts in sedimentary or alkaline igneous environments. It is highly sensitive to humidity and can dehydrate or alter when exposed to air, making it a challenging mineral for long-term preservation in collections.
Is this erdite?
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 erdite with a known reference. Erdite sits at Mohs 1.5-2 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Erdite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Erdite typically shows a resinous luster.
- 4Match the color rangeCompare against the expected color range: brownish-yellow, yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, crusts, radial aggregates.
Often confused with
Erdite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Erdite leaves yellow, Valleriite leaves black; luster reads resinous on Erdite and metallic on Valleriite.
How to tell apart: Pyrite is the harder of the two (Mohs 6-6.5 vs. 1.5-2); streak differs — Erdite leaves yellow, Pyrite leaves greenish-black to brownish-black; luster reads resinous on Erdite and metallic on Pyrite.
Often found alongside erdite
Minerals reported to co-occur with erdite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaFeS₂·2H₂O
- Mohs hardness
- 1.5-2
- Density
- 2.8 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Resinous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Crusts, Radial Aggregates
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sedimentary Deposits, Igneous Complexes
- Typical price
- $50-300 per specimen
Where rockhounds find erdite
Classic worldwide localities
- Ediacara Hills (Australia)
- Mont Saint-Hilaire (Canada)
- Khibiny Massif (Russia)
Field-hunting tip
Look in sedimentary deposits, igneous complexes country — that is the host setting where erdite typically forms. If you start seeing pyrite, marcasite, sphalerite in float, you are in the right ground. Field specimens usually show a platy crystals, crusts, radial aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find erdite on the map
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