Straczekite is a rare vanadium mineral that forms as thin, brittle, platy crystals in oxidized zones of uranium-vanadium deposits. It is typically identified by its dark, metallic-looking appearance and association with other secondary vanadium minerals in the Colorado Plateau region.
Is this straczekite?
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 straczekite with a known reference. Straczekite sits at Mohs 2, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Straczekite leaves a greenish black streak.
- 3Read the lusterHold the specimen under a strong light. Straczekite typically shows a greasy luster.
- 4Match the color rangeCompare against the expected color range: black, dark brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: platy crystals.
Often confused with
Straczekite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Straczekite leaves greenish black, Navajoite leaves yellowish-brown; luster reads greasy on Straczekite and adamantine to silky on Navajoite.
How to tell apart: Straczekite is noticeably harder (Mohs 2 vs. approx 1); streak differs, so Straczekite leaves greenish black, Hewettite leaves brownish red; luster reads greasy on Straczekite and silky to adamantine on Hewettite.
Often found alongside straczekite
Minerals reported to co-occur with straczekite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- (Ca,K,Ba)(V⁴⁺,V⁵⁺)₈O₂₀·3H₂O
- Mohs hardness
- 2
- Density
- 3.09 g/cm³
- Colors
- Streak
- Greenish Black
- Luster
- Greasy
- Transparency
- Opaque
- Crystal system
- Monoclinic
- Crystal habit
- Platy Crystals
- Cleavage
- Perfect On {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Sandstone-hosted Uranium-vanadium Deposits
Where rockhounds find straczekite
Classic worldwide localities
- Monument No. 1 mine, Apache County, Arizona, USA
- San Rafael Swell, Emery County, Utah, USA
- Various uranium-vanadium deposits in the Colorado Plateau
Field-hunting tip
Look in sandstone-hosted uranium-vanadium deposits country, the host setting where straczekite typically forms. If you start seeing tyuyamunite, carnotite, gypsum in float, you are in the right ground. Field specimens usually show a platy crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify straczekite?+
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Is straczekite safe to handle?+
What rocks look like straczekite?+
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Find straczekite on the map
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