Durangite is a rare sodium aluminum arsenate fluoride mineral often found as small, vibrant orange to red-orange crystals in rhyolite cavities. It is prized by collectors for its brilliant color but is rarely seen in large sizes, typically occurring as small prismatic to tabular crystals associated with topaz and cassiterite.
Is this durangite?
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 durangite with a known reference. Durangite sits at Mohs 5-5.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: cream-yellow to pale yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous, usually dull.
- 4Match the color rangeCompare against the expected color range: light yellow, dark green, orange red, red.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic to tabular crystals.
Often confused with
Durangite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Topaz is the harder of the two (Mohs 8 vs. 5-5.5); streak differs, so Durangite leaves cream-yellow to pale yellow, Topaz leaves white.
How to tell apart: Streak differs, so Durangite leaves cream-yellow to pale yellow, Triplite leaves white to brown.
Often found alongside durangite
Minerals reported to co-occur with durangite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaAlAsO₄F
- Mohs hardness
- 5-5.5
- Density
- 3.90-4.07 g/cm³
- Streak
- Cream-yellow to pale yellow
- Luster
- Vitreous, usually dull
- Transparency
- Transparent to opaque
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic to tabular crystals
- Cleavage
- On {110}, distinct
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In veins in alkalic rhyolite and tin placers derived therefrom; in pegmatite dikes in granite
Where rockhounds find durangite
Classic worldwide localities
- Tin prospects near Boiler Peak, in the Black Range, Sierra Co., New Mexico, USA
- Thomas Range, Juab Co., Utah, USA
- Barranca tin mine, about 30 km northeast of Coneto de Comonfort, Durango, Mexico
- Found near Lake Ramsey, New Ross, Nova Scotia, Canada
- Cheesewring quarry, Linkinhorne, Cornwall, England
Field-hunting tip
Where it forms: In veins in alkalic rhyolite and tin placers derived therefrom; in pegmatite dikes in granite. If you start seeing cassiterite, hematite, topaz in float, you are in the right ground. Typical habit: prismatic to tabular crystals. Train your eye for that shape before scanning the outcrop.
Common questions
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Find durangite on the map
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