Bobcookite is a rare sodium aluminum uranium sulfate, typically lime-green to greenish yellow. It was approved as a distinct mineral species in 2014. It was first described from Blue Lizard mine, Red Canyon, White Canyon district, San Juan County, Utah, USA.

Hardness

~2.5

Mohs

Luster

Vitreous

Streak

Very pale yellowish green

Transparency

Transparent

mineralrare

Bobcookite

Hardness: ~2.5
Luster: Vitreous
Streak: Very pale yellowish green
Transparency: Transparent

Is this bobcookite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch bobcookite with a known reference. Bobcookite sits at Mohs ~2.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: very pale yellowish green.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: lime-green, greenish yellow.
5
Look at form & habit
Crystal system: triclinic. Typical habit: acicular to fibrous sprays or crusts.

Often found alongside bobcookite

Minerals reported to co-occur with bobcookite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: NaAl(UO₂)₂(SO₄)₄·18H₂O
Mohs hardness: ~2.5
Density: 2.669 g/cm³
Colors: Lime-greenGreenish yellow
Streak: Very pale yellowish green
Luster: Vitreous
Transparency: Transparent
Crystal system: Triclinic
Crystal habit: Acicular to fibrous sprays or crusts
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: As efflorescent crusts, on the surfaces of mine walls, derived from the oxidation of primary minerals (uraninite, pyrite, chalcopyrite, bornite and covellite) in a relatively humid underground environment

Where rockhounds find bobcookite

Classic worldwide localities

Blue Lizard mine, Red Canyon, White Canyon district, San Juan County, Utah, USA

Field-hunting tip

Where it forms: As efflorescent crusts, on the surfaces of mine walls, derived from the oxidation of primary minerals (uraninite, pyrite, chalcopyrite, bornite and covellite) in a relatively humid underground environment. If you start seeing wetherillite, boyleite, chalcanthite in float, you are in the right ground. Typical habit: acicular to fibrous sprays or crusts. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify bobcookite?+

Mohs hardness is ~2.5. Luster: vitreous. The streak is very pale yellowish green. Common colors include lime-green, greenish yellow.

Where is bobcookite found?+

Notable localities include Blue Lizard mine, Red Canyon, White Canyon district, San Juan County, Utah, USA.

Is bobcookite safe to handle?+

Bobcookite contains uranium or thorium and calls for real care. Contains uranium and is radioactive; store it apart from other specimens. Wash hands thoroughly after handling and avoid creating dust.

What minerals are found with bobcookite?+

Bobcookite commonly co-occurs with Wetherillite, Boyleite, Chalcanthite, Dietrichite, Gypsum, Hexahydrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does bobcookite form in?+

Where it forms: As efflorescent crusts, on the surfaces of mine walls, derived from the oxidation of primary minerals (uraninite, pyrite, chalcopyrite, bornite and covellite) in a relatively humid underground environment. Working float back to the host body is the standard way to chase a fresh occurrence.

What is bobcookite used for?+

Bobcookite is used in collector.

Find bobcookite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.