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.

Hardness

5.5-6.5

Mohs

Luster

Metallic

Streak

Bright red to dark red

Transparency

Opaque

mineralcommonHematite family

Martite

Hardness: 5.5-6.5
Luster: Metallic
Streak: Bright red to dark red
Transparency: Opaque

Is this martite?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try 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.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: bright red to dark red.
3
Read the luster
Hold the specimen under a strong light. Luster: metallic.
4
Match the color range
Compare against the expected color range: black, dark gray.
5
Look at form & habit
Crystal 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.

mineral

Magnetite

Mohs 5.5-6.5

How to tell apart: Streak differs, so Martite leaves bright red to dark red, Magnetite leaves black.

Compare →

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
Colors: Black Dark gray
Streak: Bright red to dark red
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

Where rockhounds find martite

1 mapped spots

Classic worldwide localities

Minas Gerais, Brazil
Marquette Range, Michigan, USA
Elba, Italy
Kiruna, Sweden

Field-hunting tip

Where it forms: hydrothermal veins, contact metamorphic rocks. If you start seeing magnetite, hematite, quartz in float, you are in the right ground. Typical habit: pseudomorphous octahedral crystals. 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.

Browse 1 U.S. spots for martite →

Common questions

How do you identify martite?+

Mohs hardness is 5.5-6.5. Luster: metallic. The streak is bright red to dark red. Common colors include black, dark gray.

Where is martite found?+

Notable localities include Minas Gerais, Brazil; Marquette Range, Michigan, USA; Elba, Italy; Kiruna, Sweden.

Can I find martite in the United States?+

RockHoundR maps 1 martite rockhounding spots across 1 U.S. states. The top states are New York.

What rocks look like martite?+

Martite is most often confused with Magnetite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with martite?+

Martite commonly co-occurs with Magnetite, Hematite, Quartz, Pyrite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does martite form in?+

Where it forms: hydrothermal veins, contact metamorphic rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is martite used for?+

Martite is used in collector, educational.

Find martite on the map

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.