Eyselite is a rare secondary tellurium mineral typically found as earthy, yellowish crusts or coatings on oxidized ore specimens. It is primarily identified by its characteristic association with other rare tellurates and its distinctive occurrence in oxidized tellurium mining districts. Collectors prize it for its unique chemical composition and scarcity, usually occurring as small, inconspicuous patches rather than large, well-defined crystals.
Is this eyselite?
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 eyselite with a known reference. Eyselite sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Eyselite leaves a light yellow streak.
- 3Read the lusterHold the specimen under a strong light. Eyselite typically shows a earthy luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-orange, brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: microcrystalline aggregates.
Often confused with
Eyselite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Eyselite is noticeably harder (Mohs 3 vs. 2); streak differs — Eyselite leaves light yellow, Tellurite leaves white; luster reads earthy on Eyselite and adamantine on Tellurite.
How to tell apart: Emmonsite is the harder of the two (Mohs 5 vs. 3); streak differs — Eyselite leaves light yellow, Emmonsite leaves pale yellow; luster reads earthy on Eyselite and vitreous on Emmonsite.
Often found alongside eyselite
Minerals reported to co-occur with eyselite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe³⁺₆(Te⁴⁺O₃)₅(OH)₆·9H₂O
- Mohs hardness
- 3
- Density
- 4.26 g/cm³
- Colors
- Streak
- Light Yellow
- Luster
- Earthy
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Microcrystalline Aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Tellurium-bearing Ore Deposits
- Typical price
- $50-300 per specimen depending on size and rarity
Where rockhounds find eyselite
Classic worldwide localities
- Eisleben, Saxony-Anhalt, Germany
- Tombstone, Arizona, USA
- Moctezuma, Sonora, Mexico
Field-hunting tip
Look in oxidized tellurium-bearing ore deposits country — that is the host setting where eyselite typically forms. If you start seeing tellurite, emmonsite, quartz in float, you are in the right ground. Field specimens usually show a microcrystalline aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find eyselite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
