Melliniite is a rare nickel-iron phosphide found exclusively in iron meteorites. It typically occurs as small inclusions within the iron-nickel matrix, requiring microscopic analysis for proper identification.

Hardness

5-6

Mohs

Luster

Metallic

Streak

Grey

Transparency

Opaque

mineralrarePhosphide group family

Melliniite

Hardness: 5-6
Luster: Metallic
Streak: Grey
Transparency: Opaque

No image

Is this melliniite?

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 melliniite with a known reference. Melliniite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Melliniite leaves a grey streak.
3
Read the luster
Hold the specimen under a strong light. Melliniite typically shows a metallic luster.
4
Match the color range
Compare against the expected color range: white, gray.
5
Look at form & habit
Crystal system: cubic. Typical habit: anhedral grains, inclusions.

Often confused with

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

mineral

Schreibersite

Mohs 6.5-7

How to tell apart: Streak differs, so Melliniite leaves grey, Schreibersite leaves grey-black.

Often found alongside melliniite

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

All properties

Chemical formula: (Ni,Fe,Co)₄P
Mohs hardness: 5-6
Density: 6.12 g/cm³
Colors: White Gray
Streak: Grey
Luster: Metallic
Transparency: Opaque
Crystal system: Cubic
Crystal habit: Anhedral Grains, Inclusions
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Iron Meteorites
Typical price: n/a (extremely rare specimen material)

Where rockhounds find melliniite

Classic worldwide localities

Campo del Cielo meteorite
various iron meteorites

Field-hunting tip

Look in iron meteorites country, the host setting where melliniite typically forms. If you start seeing kamacite, taenite, schreibersite in float, you are in the right ground. Field specimens usually show a anhedral grains, inclusions habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify melliniite?+

Mohs hardness is 5-6. It typically shows a metallic luster. The streak is grey. Common colors include white, gray.

Where is melliniite found?+

Notable localities include Campo del Cielo meteorite; various iron meteorites.

How much is melliniite worth?+

Typical asking prices fall in the range of n/a (extremely rare specimen material). Quality, size, and provenance can move individual specimens well outside that range.

What rocks look like melliniite?+

Melliniite is most often confused with Schreibersite, Barringerite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with melliniite?+

Melliniite commonly co-occurs with Kamacite, Taenite, Schreibersite, Troilite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does melliniite form in?+

Melliniite typically forms in iron meteorites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is melliniite used for?+

Melliniite is used in collector.

Find melliniite on the map

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