Fornacite is a rare lead copper chromate-arsenate mineral typically found in the oxidation zones of ore deposits. It is best identified by its distinct yellowish-green color and bladed, tabular habit, often occurring alongside closely related vauquelinite.
Is this fornacite?
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 fornacite with a known reference. Fornacite sits at Mohs 3 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Fornacite leaves a yellow streak.
- 3Read the lusterHold the specimen under a strong light. Fornacite typically shows a adamantine luster.
- 4Match the color rangeCompare against the expected color range: yellow, yellow-green, brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: bladed to tabular crystals, sometimes crusts or sheaf-like aggregates.
Often confused with
Fornacite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Fornacite leaves yellow, Vauquelinite leaves greenish-yellow; luster reads adamantine on Fornacite and resinous to adamantine on Vauquelinite.
How to tell apart: Streak differs — Fornacite leaves yellow, Mimetite leaves white.
Often found alongside fornacite
Minerals reported to co-occur with fornacite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pb₂Cu(CrO₄)(AsO₄)(OH)
- Mohs hardness
- 3
- Density
- 6.2 g/cm³
- Colors
- Streak
- Yellow
- Luster
- Adamantine
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Bladed to Tabular Crystals, Sometimes Crusts or Sheaf-like Aggregates
- Cleavage
- Distinct On {110}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Hydrothermal Lead-copper-arsenic Deposits
- Typical price
- $50-500 thumbnail
Where rockhounds find fornacite
Classic worldwide localities
- Tsumeb, Namibia
- Berezovskoe, Russia
- Broken Hill, Australia
- Reid Station, Argentina
Field-hunting tip
Look in oxidized zones of hydrothermal lead-copper-arsenic deposits country — that is the host setting where fornacite typically forms. If you start seeing vauquelinite, cerussite, wulfenite in float, you are in the right ground. Field specimens usually show a bladed to tabular crystals, sometimes crusts or sheaf-like aggregates habit, so train your eye for that shape before scanning the outcrop.
Common questions
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Find fornacite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
