Hummerite is a rare hydrated potassium magnesium vanadate that typically forms as bright orange efflorescent crusts or tiny tabular crystals in oxidized zones of uranium-vanadium deposits. Due to its solubility and sensitivity to atmospheric moisture, specimens should be stored in a dry environment to prevent dehydration or degradation.

Hardness

Mohs

Luster

Vitreous

Streak

Yellow

Transparency

Translucent

mineralrare

Hummerite

Hardness: 2
Luster: Vitreous
Streak: Yellow
Transparency: Translucent

Is this hummerite?

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 hummerite with a known reference. Hummerite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Hummerite leaves a yellow streak.
3
Read the luster
Hold the specimen under a strong light. Hummerite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: orange, yellow-orange.
5
Look at form & habit
Crystal system: triclinic. Typical habit: tabular crystals, crusts, efflorescent coatings.

Often confused with

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

How to tell apart: Hummerite is noticeably harder (Mohs 2 vs. approx 1); streak differs, so Hummerite leaves yellow, Hewettite leaves brownish red; luster reads vitreous on Hummerite and pearly on Hewettite.

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Often found alongside hummerite

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

All properties

Chemical formula: K₂Mg₂(V₁₀O₂₈)·16H₂O
Mohs hardness: 2
Density: 2.44 g/cm³
Colors: Orange Yellow-orange
Streak: Yellow
Luster: Vitreous
Transparency: Translucent
Crystal system: Triclinic
Crystal habit: Tabular Crystals, Crusts, Efflorescent Coatings
Cleavage: Perfect
Rarity: Rare
Uses: Collector
Host rock: Sandstone
Typical price: $50-300 per thumbnail or small specimen

Where rockhounds find hummerite

Classic worldwide localities

Hummer Mine, Colorado, USA
La Sal Mountains, Utah, USA

Field-hunting tip

Look in sandstone country, the host setting where hummerite typically forms. If you start seeing gypsum, carnotite, tyuyamunite in float, you are in the right ground. Field specimens usually show a tabular crystals, crusts, efflorescent coatings habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify hummerite?+

Mohs hardness is 2. It typically shows a vitreous luster. The streak is yellow. Common colors include orange, yellow-orange.

Where is hummerite found?+

Notable localities include Hummer Mine, Colorado, USA; La Sal Mountains, Utah, USA.

How much is hummerite worth?+

Typical asking prices fall in the range of $50-300 per thumbnail or small specimen. Quality, size, and provenance can move individual specimens well outside that range.

Is hummerite safe to handle?+

It contains toxic constituents. Hummerite contains vanadium, which is toxic if ingested or inhaled as dust. Wash hands thoroughly after handling and avoid creating dust when cleaning specimens. Handle with care, avoid grinding or breathing dust, and store separately.

What rocks look like hummerite?+

Hummerite is most often confused with Pascoite, Hewettite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with hummerite?+

Hummerite commonly co-occurs with Gypsum, Carnotite, Tyuyamunite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does hummerite form in?+

Hummerite typically forms in sandstone. Working float back to the host body is the standard way to chase a fresh occurrence.

What is hummerite used for?+

Hummerite is used in collector.

Find hummerite on the map

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