Martite is a classic pseudomorph where hematite has replaced magnetite, preserving the original octahedral crystal shape of the magnetite. Collectors look for sharp, metallic-black octahedrons that leave a telltale reddish-brown streak rather than the black streak of its parent magnetite.
Is this martite?
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 martite with a known reference. Martite sits at Mohs 5.5-6.5 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Martite leaves a reddish brown streak.
- 3Read the lusterHold the specimen under a strong light. Martite typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: black, dark gray.
- 5Look at form & habitCrystal system: trigonal. Typical habit: pseudomorphous octahedral crystals.
Often confused with
Martite vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside martite
Minerals reported to co-occur with martite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Fe₂O₃
- Mohs hardness
- 5.5-6.5
- Density
- 5.2-5.3 g/cm³
- Streak
- Reddish Brown
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Trigonal
- Crystal habit
- Pseudomorphous Octahedral Crystals
- Cleavage
- None
- Rarity
- Common
- Uses
- Collector, Educational
- Host rock
- Hydrothermal Veins, Contact Metamorphic Rocks
- Typical price
- $5-50 for typical specimens
Where rockhounds find martite
1 mapped spotsClassic worldwide localities
- Minas Gerais, Brazil
- Marquette Range, Michigan, USA
- Elba, Italy
- Kiruna, Sweden
Field-hunting tip
Look in hydrothermal veins, contact metamorphic rocks country — that is the host setting where martite typically forms. If you start seeing magnetite, hematite, quartz in float, you are in the right ground. Field specimens usually show a pseudomorphous octahedral crystals habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in New York — start trip planning there.
Common questions
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Find martite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
