Markcooperite is an extremely rare lead-uranium silicate mineral discovered in the Musonoi Mine. It typically forms small, orange, translucent tabular crystals often found associated with other uranium-bearing secondary minerals in oxidation zones.
Is this markcooperite?
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 markcooperite with a known reference. Markcooperite sits at Mohs 3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: pale orange.
- 3Read the lusterHold the specimen under a strong light. Luster: adamantine.
- 4Match the color rangeCompare against the expected color range: orange.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular crystals, aggregates.
Often confused with
Markcooperite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Kasolite is the harder of the two (Mohs 4-5 vs. 3); luster reads adamantine on Markcooperite and subadamantine to greasy, dull to earthy when massive on Kasolite.
How to tell apart: Curite is the harder of the two (Mohs 4-5 vs. 3); streak differs, so Markcooperite leaves pale orange, Curite leaves orange.
Often found alongside markcooperite
Minerals reported to co-occur with markcooperite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₂(UO₂)TeO₆
- Mohs hardness
- 3
- Density
- 8.496 g/cm³
- Colors
- Streak
- Pale orange
- Luster
- Adamantine
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular crystals, aggregates
- Cleavage
- Perfect on {100}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary phase on fracture surfaces and in small vugs in quartz veins
Where rockhounds find markcooperite
Classic worldwide localities
- Aga mine and the Bird Nest drift, southwest flank of Otto Mountain, ~2 km northwest of Baker, San Bernardino County, California, USA
Field-hunting tip
Where it forms: A secondary phase on fracture surfaces and in small vugs in quartz veins. If you start seeing bromian chlorargyrite, iodargyrite, wulfenite in float, you are in the right ground. Typical habit: tabular crystals, aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify markcooperite?+
Where is markcooperite found?+
Is markcooperite safe to handle?+
What rocks look like markcooperite?+
What minerals are found with markcooperite?+
What kind of rock does markcooperite form in?+
What is markcooperite used for?+
Find markcooperite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
