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 2-3, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: brownish yellow.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous to resinous.
- 4Match the color rangeCompare against the expected color range: brownish black, dark red, reddish brown.
- 5Look at form & habitCrystal system: amorphous. Typical habit: amorphous.
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. 2-3); streak differs, so Yukonite leaves brownish yellow, Limonite leaves yellowish-brown; luster reads vitreous to resinous on Yukonite and submetallic to earthy on Limonite.
How to tell apart: Streak differs, so Yukonite leaves brownish yellow, Pharmacosiderite leaves yellowish green; luster reads vitreous to resinous on Yukonite and adamantine to greasy 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
- Ca₇Fe₁₅(AsO₄)₉O₁₆·25H₂O
- Mohs hardness
- 2-3
- Density
- 2.65 g/cm³
- Streak
- Brownish yellow
- Luster
- Vitreous to resinous
- Transparency
- Translucent
- Crystal system
- Amorphous
- Crystal habit
- Amorphous
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A secondary mineral typically altered from arsenopyrite
Where rockhounds find yukonite
Classic worldwide localities
- Sterling Hill, Ogdensburg, Sussex Co., New Jersey, and the Crystal No. 8 mine, Trout Creek pegmatites, Chaffee Co., Colorado, USA
- Found on the west side of Windy Arm, Tagish Lake, Yukon Territory, Canada
- Saalfeld, Thuringia, Germany
- Graulai mountain, near Lammersdorf, Eifel district, Germany
- Hasserode, near Wernigerode, Harz Mountains, Germany
- Heubachtal, Black Forest, Germany
Field-hunting tip
Where it forms: A secondary mineral typically altered from arsenopyrite. If you start seeing symplesite, argentian galena, pyrargyrite in float, you are in the right ground. Typical habit: amorphous. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify yukonite?+
Where is yukonite found?+
Is yukonite safe to handle?+
What rocks look like yukonite?+
What minerals are found with yukonite?+
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Find yukonite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
