Yukonite is a rare, amorphous hydrated calcium iron arsenate that typically forms dark, resinous botryoidal crusts or masses. It is most commonly found in the oxidized zones of arsenic-rich mineral deposits. Collectors should handle it with care due to its arsenic content.
Is this yukonite?
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 yukonite with a known reference. Yukonite sits at Mohs 2.5-3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Yukonite leaves a yellowish-brown streak.
- 3Read the lusterHold the specimen under a strong light. Yukonite typically shows a resinous luster.
- 4Match the color rangeCompare against the expected color range: black, dark brown, yellowish-brown.
- 5Look at form & habitCrystal system: amorphous. Typical habit: botryoidal, massive, crusts.
Often confused with
Yukonite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Limonite is the harder of the two (Mohs 4-5.5 vs. 2.5-3); luster reads resinous on Yukonite and submetallic to earthy on Limonite.
How to tell apart: Streak differs — Yukonite leaves yellowish-brown, Pharmacosiderite leaves white; luster reads resinous on Yukonite and adamantine on Pharmacosiderite.
Often found alongside yukonite
Minerals reported to co-occur with yukonite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Ca₂Fe³⁺₃(AsO₄)₂(OH)₅·5H₂O
- Mohs hardness
- 2.5-3
- Density
- 2.6-2.7 g/cm³
- Streak
- Yellowish-brown
- Luster
- Resinous
- Transparency
- Opaque
- Crystal system
- Amorphous
- Crystal habit
- Botryoidal, Massive, Crusts
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Arsenic-rich Hydrothermal Deposits
- Typical price
- $20-150 thumbnail to miniature specimens
Where rockhounds find yukonite
Classic worldwide localities
- Yukon Territory, Canada
- Saxony, Germany
- Guanajuato, Mexico
Field-hunting tip
Look in oxidized zones of arsenic-rich hydrothermal deposits country — that is the host setting where yukonite typically forms. If you start seeing scorodite, arsenopyrite, quartz in float, you are in the right ground. Field specimens usually show a botryoidal, massive, crusts habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find yukonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
