Coconinoite is a rare, complex hydrated iron-aluminum-uranyl phosphate mineral that typically occurs as soft, powdery, or earthy yellow coatings on sandstone. It was first discovered in the uranium-bearing deposits of the Colorado Plateau and is highly sought after by collectors of radioactive minerals due to its restricted type localities.
Is this coconinoite?
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 coconinoite with a known reference. Coconinoite sits at Mohs 1-2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: dull.
- 4Match the color rangeCompare against the expected color range: yellow, cream yellow, light yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: lath, microscopic crystals, platy.
Often confused with
Coconinoite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Coconinoite leaves white, Autunite leaves pale yellow; luster reads dull on Coconinoite and vitreous, pearly on {001} on Autunite.
How to tell apart: Streak differs, so Coconinoite leaves white, Torbernite leaves pale green; luster reads dull on Coconinoite and vitreous, subadamantine, waxy, pearly on cleavages; becoming dull on dehydration to metatorbernite on Torbernite.
Often found alongside coconinoite
Minerals reported to co-occur with coconinoite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₂Al₂(UO₂)₂(PO₄)₄(SO₄)(OH)₂·20H₂O
- Mohs hardness
- 1-2
- Density
- 2.70 g/cm³
- Colors
- Streak
- White
- Luster
- Dull
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Lath, microscopic crystals, platy
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In the oxidized zone of vanadium-poor Colorado Plateau-type U- V deposits (Utah and Arizona, USA)
Where rockhounds find coconinoite
Classic worldwide localities
- Sun Valley mine, Coconino County, Arizona, USA (type locality)
Field-hunting tip
Where it forms: In the oxidized zone of vanadium-poor Colorado Plateau-type U- V deposits (Utah and Arizona, USA). If you start seeing gypsum, jarosite, limonite in float, you are in the right ground. Typical habit: lath, microscopic crystals, platy. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify coconinoite?+
Where is coconinoite found?+
Is coconinoite safe to handle?+
What rocks look like coconinoite?+
What minerals are found with coconinoite?+
What kind of rock does coconinoite form in?+
What is coconinoite used for?+
Find coconinoite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
