Gladiusite is a rare hydrated iron phosphate mineral typically found as small, sword-like prismatic crystals. It is primarily known from the Big Fish River area of Canada, where it occurs within phosphatic iron-rich sedimentary deposits. Collectors look for its characteristic morphology and its association with other secondary phosphate minerals.
Is this gladiusite?
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 gladiusite with a known reference. Gladiusite sits at Mohs 4-4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: olive-green, (in 10-12 hours, changes to brownish red).
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: dark green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: acicular, aggregates.
Often confused with
Gladiusite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Gladiusite is noticeably harder (Mohs 4-4.5 vs. 1.5-2); streak differs, so Gladiusite leaves olive-green, (in 10-12 hours, changes to brownish red), Vivianite leaves white, altering to dark blue, brown.
How to tell apart: Streak differs, so Gladiusite leaves olive-green, (in 10-12 hours, changes to brownish red), Phosphosiderite leaves white.
Often found alongside gladiusite
Minerals reported to co-occur with gladiusite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe³⁺₂Fe²⁺₄(PO₄)(OH)₁₁·H₂O
- Mohs hardness
- 4-4.5
- Density
- 3.11 g/cm³
- Colors
- Streak
- Olive-green, (in 10-12 hours, changes to brownish red)
- Luster
- Vitreous
- Transparency
- Translucent in thin needles, opaque in aggregates
- Crystal system
- Monoclinic
- Crystal habit
- Acicular, aggregates
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- A rare (only a few hundred mg are known to exist) low-temperature hydrothermal mineral in vugs in veins of dolomitic carbonatite
Where rockhounds find gladiusite
Classic worldwide localities
- Kovdor alkaline-ultramafic complex, Kola Peninsula, Russia
Field-hunting tip
Where it forms: A rare (only a few hundred mg are known to exist) low-temperature hydrothermal mineral in vugs in veins of dolomitic carbonatite. If you start seeing pyrite, rutile, catapleiite in float, you are in the right ground. Typical habit: acicular, aggregates. Train your eye for that shape before scanning the outcrop.
Common questions
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Find gladiusite on the map
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