Wupatkiite is a rare hydrated sulfate mineral typically found as delicate, fibrous efflorescences in the arid, weathered sandstone environments of the American Southwest. It is notoriously fragile and soluble, often requiring dry, protected storage to prevent degradation or dissolution.

Hardness

1.5

Mohs

Luster

Silky in masses

Streak

White

Transparency

Semitransparent

mineralrarePickeringite Group family

Wupatkiite

Hardness: 1.5
Luster: Silky in masses
Streak: White
Transparency: Semitransparent

Is this wupatkiite?

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 wupatkiite with a known reference. Wupatkiite sits at Mohs 1.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: silky in masses.
4
Match the color range
Compare against the expected color range: light pink, pink.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: fibrous.

Often confused with

Wupatkiite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Pickeringite

Mohs 1.5

How to tell apart: Luster reads silky in masses on Wupatkiite and vitreous on Pickeringite.

How to tell apart: Luster reads silky in masses on Wupatkiite and vitreous on Halotrichite.

Often found alongside wupatkiite

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

All properties

Chemical formula: CoAl₂(SO₄)₄·22H₂O
Mohs hardness: 1.5
Density: 1.92 g/cm³
Colors: Light pink Pink
Streak: White
Luster: Silky in masses
Transparency: Semitransparent
Crystal system: Monoclinic
Crystal habit: Fibrous
Cleavage: One at 70° to fiber length
Rarity: Rare
Uses: Collector
Host rock: A rare post-mine oxidation product of sooty U–Co–Ni–Mo primary mineralization (Cameron district, Arizona, USA)

Where rockhounds find wupatkiite

Classic worldwide localities

On the walls of a shallow open cut 8 miles ESE of Gray Mountain, Coconino County, Arizona USA (type locality)

Field-hunting tip

Where it forms: A rare post-mine oxidation product of sooty U–Co–Ni–Mo primary mineralization (Cameron district, Arizona, USA). If you start seeing pickeringite, moorhouseite, nickel-boussingaultite in float, you are in the right ground. Typical habit: fibrous. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify wupatkiite?+

Mohs hardness is 1.5. Luster: silky in masses. The streak is white. Common colors include light pink, pink.

Where is wupatkiite found?+

Notable localities include On the walls of a shallow open cut 8 miles ESE of Gray Mountain, Coconino County, Arizona USA (type locality).

Is wupatkiite safe to handle?+

Wupatkiite contains cobalt. Wash your hands afterwards, never grind or breathe the dust, and store it apart from specimens you handle often.

What rocks look like wupatkiite?+

Wupatkiite is most often confused with Pickeringite, Halotrichite, Apjohnite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with wupatkiite?+

Wupatkiite commonly co-occurs with Pickeringite, Moorhouseite, Nickel-boussingaultite, Quartz, Clay. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does wupatkiite form in?+

Where it forms: A rare post-mine oxidation product of sooty U–Co–Ni–Mo primary mineralization (Cameron district, Arizona, USA). Working float back to the host body is the standard way to chase a fresh occurrence.

What is wupatkiite used for?+

Wupatkiite is used in collector.

Find wupatkiite on the map

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