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.
Is this melliniite?
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 melliniite with a known reference. Melliniite sits at Mohs 8-8.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: gray.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: creamy yellow.
- 5Look at form & habitCrystal system: cubic. Typical habit: anhedral grains.
Often confused with
Melliniite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Melliniite is noticeably harder (Mohs 8-8.5 vs. 6.5-7); streak differs, so Melliniite leaves gray, Schreibersite leaves dark gray; luster reads metallic on Melliniite and brilliant metallic on Schreibersite.
How to tell apart: Melliniite is noticeably harder (Mohs 8-8.5 vs. >7).
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)₄P
- Mohs hardness
- 8-8.5
- Density
- 7.88 g/cm³
- Colors
- Creamy yellow
- Streak
- Gray
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Anhedral grains
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector
- Host rock
- In an acapulcoite meteorite
Where rockhounds find melliniite
Classic worldwide localities
- Acapulcoite achondrite Northwest Africa 1054 (type locality)
Field-hunting tip
Where it forms: In an acapulcoite meteorite. If you start seeing kamacite, nickelphosphide in float, you are in the right ground. Typical habit: anhedral grains. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify melliniite?+
Where is melliniite found?+
Is melliniite safe to handle?+
What rocks look like melliniite?+
What minerals are found with melliniite?+
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Find melliniite on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
