Uzonite is an extremely rare arsenic sulfide mineral found primarily as a product of hot spring activity in volcanic regions. It typically appears as yellow to orange crusts or tiny needle-like crystals and is chemically similar to realgar but crystallizes in a distinct monoclinic form.
Is this uzonite?
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 uzonite with a known reference. Uzonite sits at Mohs ~1.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: pearly to slightly greasy on a broken surface.
- 4Match the color rangeCompare against the expected color range: yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: microscopic crystals, prismatic.
Often confused with
Uzonite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Uzonite leaves yellow, Realgar leaves red-orange to red; luster reads pearly to slightly greasy on a broken surface on Uzonite and resinous to greasy on Realgar.
How to tell apart: Streak differs, so Uzonite leaves yellow, Pararealgar leaves bright yellow; luster reads pearly to slightly greasy on a broken surface on Uzonite and vitreous to resinous on Pararealgar.
Often found alongside uzonite
Minerals reported to co-occur with uzonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- As₄S₅
- Mohs hardness
- ~1.5
- Density
- 3.385 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Pearly to slightly greasy on a broken surface
- Transparency
- Transparent
- Crystal system
- Monoclinic
- Crystal habit
- Microscopic crystals, prismatic
- Cleavage
- {001}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- As intergrowths with realgar in the pore spaces of tuffaceous sediments 10–30 cm deep in a caldera
Where rockhounds find uzonite
Classic worldwide localities
- Uzon caldera, Kamchatka, Russia (type locality)
Field-hunting tip
Where it forms: As intergrowths with realgar in the pore spaces of tuffaceous sediments 10–30 cm deep in a caldera. If you start seeing realgar, cubic α–arsenic sulfide, amorphous arsenic sulfide in float, you are in the right ground. Typical habit: microscopic crystals, prismatic. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify uzonite?+
Where is uzonite found?+
Is uzonite safe to handle?+
What rocks look like uzonite?+
What minerals are found with uzonite?+
What kind of rock does uzonite form in?+
What is uzonite used for?+
Find uzonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
