Yarrowite is a rare copper sulfide mineral that typically forms as an alteration product of other copper minerals. It is best identified in laboratory settings via X-ray diffraction, as it is visually indistinguishable from its associate, covellite, often appearing as dark, metallic-lustered inclusions or fine-grained masses.
Is this yarrowite?
4-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 yarrowite with a known reference. Yarrowite sits at Mohs 3.5, softer than the next harder reference, harder than the previous one.
- 2Read the lusterHold the specimen under a strong light. Luster: metallic.
- 3Match the color rangeCompare against the expected color range: black, blue.
- 4Look at form & habitCrystal system: trigonal. Typical habit: massive, stellate, tarnishes.
Often confused with
Yarrowite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Yarrowite is noticeably harder (Mohs 3.5 vs. 1.5-2); luster reads metallic on Yarrowite and submetallic, inclining to resinous, somewhat pearly on cleavage; subresinous to dull when massive on Covellite.
Often found alongside yarrowite
Minerals reported to co-occur with yarrowite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Cu₉S₈
- Mohs hardness
- 3.5
- Density
- 4.89 g/cm³
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Massive, stellate, tarnishes
- Cleavage
- {0001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As weathering-produced lamellar replacements of other copper sulfides in stratabound red-bed copper deposits (Yarrow and Spionkop Creeks, Canada)
Where rockhounds find yarrowite
Classic worldwide localities
- High Rolls district, Otero Co., New Mexico, and at Washington Pass, Okanogan Co., Washington, USA
- Upper Grinnell Formation, Spionkop Creek and Yarrow Creek areas of southwestern Alberta, Canada
- Cannington Park, Bridgwater, Somerset, England
- Lubin and Rudna copper mines, near Legnica, Zechstein copper district, Lower Silesia, Poland
Field-hunting tip
Where it forms: As weathering-produced lamellar replacements of other copper sulfides in stratabound red-bed copper deposits (Yarrow and Spionkop Creeks, Canada). If you start seeing anilite, djurleite, spionkopite in float, you are in the right ground. Typical habit: massive, stellate, tarnishes. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify yarrowite?+
Where is yarrowite found?+
Is yarrowite safe to handle?+
What rocks look like yarrowite?+
What minerals are found with yarrowite?+
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Find yarrowite on the map
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