Gatewayite is a calcium arsenic vanadium oxide, typically very dark greenish blue. It is a secondary mineral formed by the oxidation of montroseite-corvusite assemblages in a moist environment. It was first described from Packrat mine, Gateway district, Mesa County, Colorado, USA.
Is this gatewayite?
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 gatewayite with a known reference. Gatewayite sits at Mohs 7, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Gatewayite leaves a grayish blue streak.
- 3Read the lusterHold the specimen under a strong light. Gatewayite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark greenish blue.
- 5Look at form & habitCrystal system: trigonal. Typical habit: massive.
Often confused with
Gatewayite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Gatewayite leaves grayish blue, Flint Nodule leaves white; luster reads vitreous on Gatewayite and waxy on Flint Nodule.
How to tell apart: Streak differs, so Gatewayite leaves grayish blue, Chalcedony leaves white; luster reads vitreous on Gatewayite and waxy on Chalcedony.
How to tell apart: Streak differs, so Gatewayite leaves grayish blue, Jasper leaves white; luster reads vitreous on Gatewayite and waxy on Jasper.
Often found alongside gatewayite
Minerals reported to co-occur with gatewayite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₆(As³⁺V⁴⁺₃V⁵⁺₉As⁵⁺₆O₅₁)·31H₂O
- Mohs hardness
- 7
- Density
- 2.34 g/cm³
- Colors
- Streak
- Grayish Blue
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Trigonal
- Crystal habit
- Massive
- Cleavage
- Fair On {010} and {101}
- Rarity
- Common
- Uses
- Lapidary, Collector
- Host rock
- Sedimentary Formations
Where rockhounds find gatewayite
Classic worldwide localities
- Gateway, Colorado, USA
Field-hunting tip
Look in sedimentary formations country, the host setting where gatewayite typically forms. If you start seeing quartz, calcite, barite in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find gatewayite on the map
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