Stanfieldite is a rare phosphate mineral primarily known for its occurrence in stony-iron meteorites like pallasites. It typically forms as small, microscopic inclusions within the silicate and metallic phases of these extraterrestrial rocks.

Hardness

4.5-5

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareWhitlockite Group family

Stanfieldite

Hardness: 4.5-5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this stanfieldite?

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 stanfieldite with a known reference. Stanfieldite sits at Mohs 4.5-5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: yellow brown, reddish yellow.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: anhedral grains.

Often confused with

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

Often found alongside stanfieldite

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

All properties

Chemical formula: Ca₄Mg₅(PO₄)₆
Mohs hardness: 4.5-5
Density: 3.15 g/cm³
Colors: Yellow brown Reddish yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Anhedral grains
Cleavage: None
Rarity: Rare
Uses: Collector, Scientific research
Host rock: A rare component of some meteorites

Where rockhounds find stanfieldite

Classic worldwide localities

Estherville mesosiderite meteorite, and the pallasite meteorites Albin, Finmarken, Imilac, Newport, Mount Vernon, Santa Rosalia, and Zaisho

Field-hunting tip

Where it forms: A rare component of some meteorites. If you start seeing olivine, whitlockite, farringtonite 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 stanfieldite?+

Mohs hardness is 4.5-5. Luster: vitreous. The streak is white. Common colors include yellow brown, reddish yellow.

Where is stanfieldite found?+

Notable localities include Estherville mesosiderite meteorite, and the pallasite meteorites Albin, Finmarken, Imilac, Newport, Mount Vernon, Santa Rosalia, and Zaisho.

What rocks look like stanfieldite?+

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

What minerals are found with stanfieldite?+

Stanfieldite commonly co-occurs with Olivine, Whitlockite, Farringtonite, Troilite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does stanfieldite form in?+

Where it forms: A rare component of some meteorites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is stanfieldite used for?+

Stanfieldite is used in collector, scientific research.

Find stanfieldite on the map

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