Stromeyerite is a rare silver-copper sulfide that typically appears as dark, metallic, steel-gray masses. Collectors look for its characteristic tarnish, which can develop a slight iridescent blue or purple sheen over time. It is primarily found in hydrothermal veins alongside other silver and copper-bearing sulfides.
Is this stromeyerite?
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 stromeyerite with a known reference. Stromeyerite sits at Mohs 2.5-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: steel-gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: steel gray, blue gray, dark blue, dark steel gray.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: granular, massive, pseudo hexagonal.
Often confused with
Stromeyerite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Stromeyerite leaves steel-gray, Chalcocite leaves blackish lead-gray.
How to tell apart: Streak differs, so Stromeyerite leaves steel-gray, Argentite leaves black.
How to tell apart: Streak differs, so Stromeyerite leaves steel-gray, Tetrahedrite leaves black to brown.
Often found alongside stromeyerite
Minerals reported to co-occur with stromeyerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- AgCuS
- Mohs hardness
- 2.5-3
- Density
- 6.2-6.3 g/cm³
- Colors
- Streak
- Steel-gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Granular, massive, pseudo hexagonal
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Ore of silver
- Host rock
- In hydrothermal veins, formed most commonly by secondary processes, although it also forms as a primary mineral
Where rockhounds find stromeyerite
Classic worldwide localities
- Silver King and Magma mines, Superior, Pinal Co., Arizona, USA
- Red Mountain district, San Juan Co., Colorado, USA
- American Sisters mine, Clear Creek Co., Colorado, USA
- Butte, Silver Bow Co., Montana, USA
- Zmeyewskaja-Goro, near Zmeinogorsk (Schlangenberg), Altai Mountains, Siberia, Russia (type locality)
- Dzhezkazgan, Kazakhstan
Field-hunting tip
Where it forms: In hydrothermal veins, formed most commonly by secondary processes, although it also forms as a primary mineral. If you start seeing freibergite, bornite, chalcopyrite in float, you are in the right ground. Typical habit: granular, massive, pseudo hexagonal. Train your eye for that shape before scanning the outcrop.
Common questions
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Find stromeyerite on the map
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