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. Streak: pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: yellow, greenish yellow.
- 5Look at form & habitCrystal system: triclinic. Typical habit: mammillary.
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); luster reads vitreous on Emmonsite and subadamantine to vitreous, resinous on fractures on Jarosite.
How to tell apart: Emmonsite is noticeably harder (Mohs ~5 vs. 3); luster reads vitreous on Emmonsite and pearly to dull on Quetzalcoatlite.
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
- 4.52-4.55 g/cm³
- Colors
- Streak
- Pale yellow
- Luster
- Vitreous
- Transparency
- Opaque to translucent, transparent in small grains
- Crystal system
- Triclinic
- Crystal habit
- Mammillary
- Cleavage
- Perfect on {010}; good on {100} and {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- An alteration product formed from earlier tellurium minerals in the oxide zone of some hydrothermal precious metal deposits
Where rockhounds find emmonsite
Classic worldwide localities
- W.P.H., Moose, and Deadwood mines, Cripple Creek, Teller Co., Colorado, USA
- Toughnut-Empire mine and between the Joe and Grand Central mines, Tombstone, Cochise Co., Arizona, USA
- Wilcox district, Catron Co., and the Sylvanite district, Hidalgo Co., New Mexico, USA
- Mohawk mine, Goldfield, Esmeralda Co., Nevada, USA
- Moctezuma (Bambolla) mine, 12 km south of Moctezuma, Sonora, Mexico
- El Plomo mine, Tegucigalpa, Honduras
Field-hunting tip
Where it forms: An alteration product formed from earlier tellurium minerals in the oxide zone of some hydrothermal precious metal deposits. If you start seeing tellurium, tellurite, rodalquilarite in float, you are in the right ground. Typical habit: mammillary. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify emmonsite?+
Where is emmonsite found?+
Is emmonsite safe to handle?+
What rocks look like emmonsite?+
What minerals are found with emmonsite?+
What kind of rock does emmonsite form in?+
What is emmonsite used for?+
Find emmonsite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
