Geerite is a very rare copper sulfide mineral typically found as microscopic grains within supergene enrichment zones. It is nearly impossible to distinguish from other copper sulfides like chalcocite without laboratory analysis such as X-ray diffraction or electron microprobe data. It is primarily a mineralogical curiosity for advanced collectors specializing in secondary copper ores.
Is this geerite?
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 geerite with a known reference. Geerite sits at Mohs <3.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: white, blue gray.
- 5Look at form & habitCrystal system: trigonal. Typical habit: platy.
Often confused with
Geerite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Geerite leaves black, Chalcocite leaves blackish lead-gray.
How to tell apart: Streak differs, so Geerite leaves black, Digenite leaves grayish black; luster reads metallic on Geerite and submetallic on Digenite.
How to tell apart: Streak differs, so Geerite leaves black, Djurleite leaves metallic.
Often found alongside geerite
Minerals reported to co-occur with geerite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₈S₅
- Mohs hardness
- <3.5
- Density
- 5.61 g/cm³
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Platy
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Replacing sphalerite along cleavage traces (DeKalb Township, New York, USA); in a serpentine-hosted magnetite–chromite deposit (Eretria, Greece)
Where rockhounds find geerite
Classic worldwide localities
- DeKalb Township, St. Lawrence Co., New York (type locality), and at Cuchillo, Winston district, Sierra Co., New Mexico, USA
- Eretria, Othris Mountains, Greece
- Lubin and Rudna copper mines, near Legnica, Zechstein copper district, Lower Silesia, Poland
- Clara mine, near Oberwolfach, Black Forest, Germany
- Southwestern Co. Cork, Ireland
- Lorena gold deposit, near Cloncurry, Queensland, Australia
Field-hunting tip
Where it forms: Replacing sphalerite along cleavage traces (DeKalb Township, New York, USA); in a serpentine-hosted magnetite–chromite deposit (Eretria, Greece). If you start seeing spionkopite, sphalerite, tetrahedrite in float, you are in the right ground. Typical habit: platy. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify geerite?+
Where is geerite found?+
Is geerite safe to handle?+
What rocks look like geerite?+
What minerals are found with geerite?+
What kind of rock does geerite form in?+
What is geerite used for?+
Find geerite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
