Xanthiosite is a rare nickel arsenate mineral typically found as secondary crusts or delicate acicular aggregates in oxidized hydrothermal nickel-arsenic veins. It is distinguished by its bright, characteristic yellow color, though it is often confused with other secondary nickel minerals that form in similar oxidation zones.
Is this xanthiosite?
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 xanthiosite with a known reference. Xanthiosite sits at Mohs 4, 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: resinous.
- 4Match the color rangeCompare against the expected color range: golden yellow.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: crusts, acicular aggregates.
Often confused with
Xanthiosite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Xanthiosite is noticeably harder (Mohs 4 vs. 1.5-2.5); streak differs, so Xanthiosite leaves yellow, Annabergite leaves pale green to white; luster reads resinous on Xanthiosite and subadamantine, pearly on cleavages, may be dull, earthy on Annabergite.
How to tell apart: Xanthiosite is noticeably harder (Mohs 4 vs. 2-2.5); streak differs, so Xanthiosite leaves yellow, Morenosite leaves pale green to white; luster reads resinous on Xanthiosite and vitreous on Morenosite.
Often found alongside xanthiosite
Minerals reported to co-occur with xanthiosite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ni₃(AsO₄)₂
- Mohs hardness
- 4
- Density
- 4.98-5.42 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Resinous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Crusts, acicular aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare secondary mineral in hydrothermal Ni–As–U ore deposits
Where rockhounds find xanthiosite
Classic worldwide localities
- Johanngeorgenstadt, Saxony, Germany
- South Terras mine, St. Stephen-in-Brannel, Cornwall, England
Field-hunting tip
Where it forms: A rare secondary mineral in hydrothermal Ni–As–U ore deposits. If you start seeing bismuth, bunsenite, aerugite in float, you are in the right ground. Typical habit: crusts, acicular aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify xanthiosite?+
Where is xanthiosite found?+
Is xanthiosite safe to handle?+
What rocks look like xanthiosite?+
What minerals are found with xanthiosite?+
What kind of rock does xanthiosite form in?+
What is xanthiosite used for?+
Find xanthiosite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
