Nagyágite is a rare and distinct lead-gold telluride mineral prized by collectors for its unique foliated or leaf-like crystal habit. It is most famous for its occurrence in the hydrothermal vein systems of Romania, where it often appears as flexible, metallic-lustered plates that can be mistaken for molybdenite. Collectors should handle it with care due to its heavy metal content and avoid creating dust during specimen cleaning.
Is this nagyágite?
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 nagyágite with a known reference. Nagyágite sits at Mohs 1.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: blackish lead-gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic, bright on fresh cleavage.
- 4Match the color rangeCompare against the expected color range: black, lead gray.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: granular, lamellar, platy.
Often confused with
Nagyágite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Nagyágite leaves blackish lead-gray, Molybdenite leaves bluish gray.
How to tell apart: Altaite is the harder of the two (Mohs 3 vs. 1.5); streak differs, so Nagyágite leaves blackish lead-gray, Altaite leaves black.
How to tell apart: Streak differs, so Nagyágite leaves blackish lead-gray, Sylvanite leaves steel-gray to silver-white.
Often found alongside nagyágite
Minerals reported to co-occur with nagyágite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₅Au(Te,Sb)₄S₅-₈
- Mohs hardness
- 1.5
- Density
- 7.35-7.49 g/cm³
- Streak
- Blackish lead-gray
- Luster
- Metallic, bright on fresh cleavage
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Granular, lamellar, platy
- Cleavage
- Perfect on {010}, excellent on {101}
- Rarity
- Uncommon
- Uses
- Collector, Scientific research
- Host rock
- In Au–Te-bearing epithermal hydrothermal veins
Where rockhounds find nagyágite
Classic worldwide localities
- Gold Hill, Boulder Co., and Cripple Creek, Teller Co., Colorado, USA
- Dorleska mine, Coffee Creek district, Trinity Co., California, USA
- Mayflower mine, Tobacco Root Mountains, Madison Co., Montana, USA
- Foote mine, Kings Mountain, Cleveland Co., North Carolina, USA
- Bohuliby mine, Jílové gold deposit, Czech Republic
- Chelopech deposit, Sofia, Bulgaria
Field-hunting tip
Where it forms: In Au–Te-bearing epithermal hydrothermal veins. If you start seeing altaite, petzite, stutzite in float, you are in the right ground. Typical habit: granular, lamellar, platy. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify nagyágite?+
Where is nagyágite found?+
Is nagyágite safe to handle?+
What rocks look like nagyágite?+
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Find nagyágite on the map
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