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 — 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 — that is 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.