Austinite is an attractive secondary arsenic mineral often found as radiating, acicular sprays or botryoidal crusts. It is most easily identified by its vibrant yellow-green fluorescence under short-wave ultraviolet light, which makes it a favorite among collectors of fluorescent minerals.
Is this austinite?
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 austinite with a known reference. Austinite sits at Mohs 4-4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: white.
- 3Read the lusterHold the specimen under a strong light. Luster: subadamantine to silky in aggregates.
- 4Match the color rangeCompare against the expected color range: colorless, brown, green, yellowish white, white.
- 5Look at form & habitCrystal system: orthorhombic. Typical habit: acicular, radiating clusters, botryoidal, crusts.
Often confused with
Austinite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Austinite leaves white, Conichalcite leaves green; luster reads subadamantine to silky in aggregates on Austinite and vitreous to somewhat greasy on Conichalcite.
How to tell apart: Luster reads subadamantine to silky in aggregates on Austinite and resinous on Adelite.
How to tell apart: Streak differs, so Austinite leaves white, Descloizite leaves orange to brownish red; luster reads subadamantine to silky in aggregates on Austinite and greasy on Descloizite.
Often found alongside austinite
Minerals reported to co-occur with austinite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- CaZn(AsO₄)(OH)
- Mohs hardness
- 4-4.5
- Density
- 4.13 g/cm³
- Streak
- White
- Luster
- Subadamantine to silky in aggregates
- Transparency
- Translucent to transparent
- Crystal system
- Orthorhombic
- Crystal habit
- Acicular, radiating clusters, botryoidal, crusts
- Cleavage
- Good on {011}
- Fluorescence
- Bright yellow-green under SW UV
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- A rare secondary mineral in the oxidized zone of some arsenic-rich base-metal deposits
Where rockhounds find austinite
Classic worldwide localities
- Western Utah mine, Gold Hill, Tooele Co., USA
- Mohawk mine, Clark Mountains, San Bernardino Co., California, USA
- Table Mountain mine, Galiuro Mountains, Pinal Co., Arizona, USA
- Sterling Hill, Ogdensburg, Sussex Co., New Jersey, USA
- Ojuela mine, Mapimí, Durango, Mexico
- Lili mine, near Lomitos, Bolivia
Field-hunting tip
Where it forms: A rare secondary mineral in the oxidized zone of some arsenic-rich base-metal deposits. If you start seeing adamite, talmessite, limonite in float, you are in the right ground. Typical habit: acicular, radiating clusters, botryoidal, crusts. Train your eye for that shape before scanning the outcrop.
Common questions
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Find austinite on the map
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