Mesosiderites are a complex class of stony-iron meteorites characterized by an approximately equal mixture of silicate minerals and metallic nickel-iron. They are easily identified by their brecciated appearance, featuring dark, angular silicate fragments embedded within a bright, metallic matrix. Collectors should look for their distinct high density compared to terrestrial rocks and the characteristic Widmanstätten patterns sometimes visible in the iron components.

Hardness

5-6

Mohs

Luster

Metallic

Streak

None, or a weak grayish streak if pressed hard

Transparency

Opaque

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Mesosiderite

Hardness: 5-6
Luster: Metallic
Streak: None, or a weak grayish streak if pressed hard
Transparency: Opaque

Is this mesosiderite?

6-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 mesosiderite with a known reference. Mesosiderite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
2
Read the texture
Look at a fresh break with a hand lens. Texture: Breccia; metal and silicate as lumps, pebbles and fine intergrowths.
3
Pick out the minerals
Composition: About equal parts nickel-iron metal and silicate (olivine, pyroxenes and calcium-rich feldspar). Identify the two or three most abundant grains.
4
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: none, or a weak grayish streak if pressed hard.
5
Read the luster
Hold the specimen under a strong light. Luster: metallic.
6
Match the color range
Compare against the expected color range: silver, gray, black, brown.

Often confused with

Mesosiderite vs. its common look-alikes, and how to tell them apart in the field.

Often found alongside mesosiderite

Minerals reported to co-occur with mesosiderite. Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Mohs hardness: 5-6
Density: 4.2-4.8 g/cm³
Colors: Silver Gray Black Brown
Streak: None, or a weak grayish streak if pressed hard
Luster: Metallic
Transparency: Opaque
Rarity: Rare
Uses: Collector, Scientific research
Host rock: Stony-Iron Meteorite
Texture: Breccia; metal and silicate as lumps, pebbles and fine intergrowths
Composition: About equal parts nickel-iron metal and silicate (olivine, pyroxenes and calcium-rich feldspar)

Where rockhounds find mesosiderite

Classic worldwide localities

Vaca Muerta (Chile)
Estherville (USA)
Lowicz (Poland)
Patwar (India)

Field-hunting tip

Where it forms: Stony-Iron Meteorite. If you start seeing olivine, pyroxene, nickel-iron in float, you are in the right ground.

Common questions

How do you identify mesosiderite?+

Mohs hardness is 5-6. Texture: Breccia; metal and silicate as lumps, pebbles and fine intergrowths. Composition: About equal parts nickel-iron metal and silicate (olivine, pyroxenes and calcium-rich feldspar). Luster: metallic. The streak is none, or a weak grayish streak if pressed hard. Common colors include silver, gray, black, brown.

Where is mesosiderite found?+

Notable localities include Vaca Muerta (Chile); Estherville (USA); Lowicz (Poland); Patwar (India).

What rocks look like mesosiderite?+

Mesosiderite is most often confused with Pallasite, Iron Meteorite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with mesosiderite?+

Mesosiderite commonly co-occurs with Olivine, Pyroxene, Nickel-Iron, Troilite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does mesosiderite form in?+

Where it forms: Stony-Iron Meteorite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is mesosiderite used for?+

Mesosiderite is used in collector, scientific research.

Find mesosiderite on the map

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