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 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: copper red, red, black.
- 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.
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
- 2
- Density
- 2.2 g/cm³
- Colors
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque, transmits light in very fine fibers
- Crystal system
- Monoclinic
- Crystal habit
- Platy crystals, crusts, radial aggregates
- Cleavage
- Good on {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Found in abundance, typically associated with other sulfides and fine grained magnetite, in discrete, late segregations within an alkalic mafic diatreme (Coyote Peak, California, USA)
Where rockhounds find erdite
Classic worldwide localities
- Coyote Peak, near Orick, Humboldt Co., California, USA (type locality)
- Mt. Alluaiv, Lovozero massif, Kola Peninsula, Russia
- Mont Saint-Hilaire and near Saint-Amable, Quebec, Canada
Field-hunting tip
Where it forms: Found in abundance, typically associated with other sulfides and fine grained magnetite, in discrete, late segregations within an alkalic mafic diatreme (Coyote Peak, California, USA). If you start seeing pyrrhotite, magnetite, rasvumite in float, you are in the right ground. Typical habit: platy crystals, crusts, radial aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify erdite?+
Where is erdite found?+
Is erdite safe to handle?+
What rocks look like erdite?+
What minerals are found with erdite?+
What kind of rock does erdite form in?+
What is erdite used for?+
Find erdite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
