Ferrisymplesite is a rare secondary mineral formed by the oxidation of arsenopyrite in mineral deposits. It is typically found as small, brownish acicular or prismatic crystals and is prized primarily by advanced mineral collectors of arsenate species.
Is this ferrisymplesite?
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 ferrisymplesite with a known reference. Ferrisymplesite 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. Ferrisymplesite leaves a brown streak.
- 3Read the lusterHold the specimen under a strong light. Ferrisymplesite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark brown, brownish black, brown.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular to prismatic crystals.
Often confused with
Ferrisymplesite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Ferrisymplesite leaves brown, Symplesite leaves white; luster reads vitreous on Ferrisymplesite and pearly on Symplesite.
How to tell apart: Streak differs — Ferrisymplesite leaves brown, Vivianite leaves white to light blue.
Often found alongside ferrisymplesite
Minerals reported to co-occur with ferrisymplesite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe³⁺₃(AsO₄)₂(OH)₃·5H₂O
- Mohs hardness
- 2-3
- Density
- 3.37 g/cm³
- Streak
- Brown
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Acicular to Prismatic Crystals
- Cleavage
- Perfect On {010}
- Rarity
- Rare
- Uses
- Collector
- Host rock
- Oxidized Zones of Arsenic-rich Hydrothermal Mineral Deposits
- Typical price
- $20-150 thumbnail to miniature
Where rockhounds find ferrisymplesite
Classic worldwide localities
- Mapimi, Mexico
- Cornwall, England
- Laurion, Greece
Field-hunting tip
Look in oxidized zones of arsenic-rich hydrothermal mineral deposits country — that is the host setting where ferrisymplesite typically forms. If you start seeing arsenopyrite, scorodite, pharmacosiderite in float, you are in the right ground. Field specimens usually show a acicular to prismatic crystals habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify ferrisymplesite?+
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What minerals are found with ferrisymplesite?+
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Find ferrisymplesite on the map
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