Hewettite is a rare, soft vanadium mineral that typically forms as delicate, dark red needle-like crystals or powdery coatings. It is primarily found in the oxidized zones of uranium-vanadium deposits, often forming as a result of the alteration of other vanadium species. Collectors prize it for its intense color, though its extreme fragility and solubility require careful handling.
Is this hewettite?
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 hewettite with a known reference. Hewettite sits at Mohs ~1, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brownish red.
- 3Read the lusterHold the specimen under a strong light. Luster: silky to adamantine.
- 4Match the color rangeCompare against the expected color range: red.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular.
Often confused with
Hewettite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Vanoxite is the harder of the two (Mohs 2-3 vs. ~1); streak differs, so Hewettite leaves brownish red, Vanoxite leaves brown black; luster reads silky to adamantine on Hewettite and metallic on Vanoxite.
How to tell apart: Steigerite is the harder of the two (Mohs 2.5-3 vs. ~1); streak differs, so Hewettite leaves brownish red, Steigerite leaves yellow; luster reads silky to adamantine on Hewettite and waxy in compact aggregates on Steigerite.
How to tell apart: Pascoite is the harder of the two (Mohs ~2.5 vs. ~1); streak differs, so Hewettite leaves brownish red, Pascoite leaves cadmium-yellow; luster reads silky to adamantine on Hewettite and vitreous to subadamantine on Pascoite.
Often found alongside hewettite
Minerals reported to co-occur with hewettite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaV₆O₁₆·9H₂O
- Mohs hardness
- ~1
- Density
- 2.51-2.61 g/cm³
- Colors
- Streak
- Brownish red
- Luster
- Silky to adamantine
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular
- Cleavage
- Perfect
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As an alteration product of patronite (Minasragra, Peru); an alteration product of less-oxidized vanadium minerals in Colorado Plateau-type U–V deposits
Where rockhounds find hewettite
Classic worldwide localities
- Jo Dandy mine, Bull Canyon district, Paradox Valley, Uravan district, Montrose Co., Colorado, USA
- Cactus Rat mine group, Yellow Cat district, 24 km southeast of Thompson, Grand Co., Utah, USA
- Long fibers from the Monument No. 2 mine, Monument Valley, also in the Carrizo and Lukachukai Mountains, Apache Co., and in the Monument No. 1 and Mitten No. 2 mines, Navajo Co., Arizona, USA
- Gold Quarry mine, near Carlin, Maggie Creek district, Eureka Co., Nevada, USA
- Minasragra, 46 km from Cerro de Pasco, Peru
Field-hunting tip
Where it forms: As an alteration product of patronite (Minasragra, Peru); an alteration product of less-oxidized vanadium minerals in Colorado Plateau-type U–V deposits. If you start seeing metahewettite, corvusite, montroseite in float, you are in the right ground. Typical habit: acicular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hewettite?+
Where is hewettite found?+
Is hewettite safe to handle?+
What rocks look like hewettite?+
What minerals are found with hewettite?+
What kind of rock does hewettite form in?+
What is hewettite used for?+
Find hewettite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
