Emmonsite is a rare hydrated iron tellurite mineral typically found as a secondary oxidation product in tellurium-rich ore deposits. It usually appears as vibrant yellow-green crusts or small, thin platy crystals that are prized by advanced micromount and systematic collectors.
Is this emmonsite?
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 emmonsite with a known reference. Emmonsite sits at Mohs 5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Emmonsite leaves a pale yellow streak.
- 3Read the lusterHold the specimen under a strong light. Emmonsite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: yellow-green, yellow, greenish-yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals, granular aggregates, crusts.
Often confused with
Emmonsite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Emmonsite is noticeably harder (Mohs 5 vs. 2.5-3.5); streak differs — Emmonsite leaves pale yellow, Jarosite leaves yellow.
How to tell apart: Emmonsite is noticeably harder (Mohs 5 vs. 3); streak differs — Emmonsite leaves pale yellow, Quetzalcoatlite leaves yellow.
Often found alongside emmonsite
Minerals reported to co-occur with emmonsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₂Te₃O₉·2H₂O
- Mohs hardness
- 5
- Density
- 6.05 g/cm³
- Streak
- Pale Yellow
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals, Granular Aggregates, Crusts
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Tellurium-bearing Hydrothermal Gold-silver Deposits
- Typical price
- $50-300 per specimen depending on size and crystal quality
Where rockhounds find emmonsite
Classic worldwide localities
- Tombstone, Arizona, USA
- Moctezuma, Sonora, Mexico
- Goldfield, Nevada, USA
- Bajo de la Alumbrera, Argentina
Field-hunting tip
Look in oxidized zones of tellurium-bearing hydrothermal gold-silver deposits country — that is the host setting where emmonsite typically forms. If you start seeing tellurite, paratellurite, eztlite in float, you are in the right ground. Field specimens usually show a platy crystals, granular aggregates, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find emmonsite on the map
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