Corkite is a rare phosphate-sulfate mineral that typically forms as a secondary mineral in the oxidized zones of lead-bearing ore deposits. It is most often found as small, yellowish-brown rhombohedral crystals or crusts coating other ores and is prized by micromount collectors.
Is this corkite?
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 corkite with a known reference. Corkite sits at Mohs 3.5-4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to resinous.
- 4Match the color rangeCompare against the expected color range: brownish yellow, yellow green, light yellow, dark green.
- 5Look at form & habitCrystal system: trigonal. Typical habit: rhombohedral crystals, pseudocubic, crusts, earthy aggregates.
Often confused with
Corkite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Corkite leaves yellow, Beudantite leaves grayish yellow to green.
How to tell apart: Streak differs, so Corkite leaves yellow, Jarosite leaves pale yellow; luster reads vitreous to resinous on Corkite and subadamantine to vitreous, resinous on fractures on Jarosite.
How to tell apart: Corkite is noticeably harder (Mohs 3.5-4.5 vs. 1.5-2); streak differs, so Corkite leaves yellow, Plumbojarosite leaves pale brown.
Often found alongside corkite
Minerals reported to co-occur with corkite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- PbFe₃(PO₄)(SO₄)(OH)₆
- Mohs hardness
- 3.5-4.5
- Density
- 4.295 g/cm³
- Streak
- Yellow
- Luster
- Vitreous to resinous
- Transparency
- Transparent
- Crystal system
- Trigonal
- Crystal habit
- Rhombohedral crystals, pseudocubic, crusts, earthy aggregates
- Cleavage
- Perfect on {0001}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- A rare secondary mineral formed at low temperatures or by weathering in oxidized hydrothermal base-metal deposits
Where rockhounds find corkite
Classic worldwide localities
- Silver Queen mine, Galena, Lawrence Co., South Dakota, USA
- Wild Bill, Harrington-Hickory, and other mines, Beaver Co., and the Gold Hill and Honerine mines, Tooele Co., Utah, USA
- Mex-Tex mine, near Bingham, Hansonburg district, Socorro Co., New Mexico, USA
- Glandore iron mines, Co. Cork, Ireland
- Mexico mine, Caldbeck Fells, Cumbria, England
- Cornwall, from the Penberthy Croft mine, St. Hilary, at Wheal Unity, Gwennap, and the Gravel Hill mine, Perranzabuloe, England
Field-hunting tip
Where it forms: A rare secondary mineral formed at low temperatures or by weathering in oxidized hydrothermal base-metal deposits. If you start seeing pyromorphite, malachite, plumbojarosite in float, you are in the right ground. Typical habit: rhombohedral crystals, pseudocubic, crusts, earthy aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify corkite?+
Where is corkite found?+
Is corkite safe to handle?+
What rocks look like corkite?+
What minerals are found with corkite?+
What kind of rock does corkite form in?+
What is corkite used for?+
Find corkite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
