Haycockite is a rare copper-iron sulfide that typically occurs as microscopic exsolution lamellae within chalcopyrite. It is best identified through reflected light microscopy in polished sections due to its strong anisotropy and similar appearance to chalcopyrite in hand specimens.
Is this haycockite?
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 haycockite with a known reference. Haycockite sits at Mohs 4.5, 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: brass yellow, metallic.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: microscopic crystals.
Often confused with
Haycockite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Haycockite leaves black, Chalcopyrite leaves greenish black.
How to tell apart: Haycockite is noticeably harder (Mohs 4.5 vs. 3.5).
How to tell apart: Haycockite is noticeably harder (Mohs 4.5 vs. 3-3.25); streak differs, so Haycockite leaves black, Bornite leaves pale grayish black.
Often found alongside haycockite
Minerals reported to co-occur with haycockite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₄Fe₅S₈
- Mohs hardness
- 4.5
- Density
- 4.35 g/cm³
- Colors
- Brass yellowMetallic
- Streak
- Black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Orthorhombic
- Crystal habit
- Microscopic crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In a hortonolite dunite (replacement) pegmatite in the Bushveld complex (Mooihoek mine, South Africa)
Where rockhounds find haycockite
Classic worldwide localities
- Basal Duluth Gabbro complex, near Hibbing, St. Louis Co., Minnesota, USA
- Bushveld complex, Transvaal, from the Mooihoek mine, Lydenburg district (type locality), and in the Townlands ultramafic pipe, Rustenburg, South Africa
- Krzemianka, Poland
- Talnakh area, Noril’sk region, western Siberia, Russia
- Madera, Sonora, Mexico
Field-hunting tip
Where it forms: In a hortonolite dunite (replacement) pegmatite in the Bushveld complex (Mooihoek mine, South Africa). If you start seeing mooihoekite, copper, troilite in float, you are in the right ground. Typical habit: microscopic crystals. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify haycockite?+
Where is haycockite found?+
Is haycockite safe to handle?+
What rocks look like haycockite?+
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Find haycockite on the map
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