Isoferroplatinum is a rare platinum-iron alloy typically occurring as small metallic grains within mafic and ultramafic igneous complexes. It is distinguished from native platinum by its high iron content and distinct optical properties under reflected light, often requiring microprobe analysis for positive identification.
Is this isoferroplatinum?
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 isoferroplatinum with a known reference. Isoferroplatinum sits at Mohs 5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: grayish-black.
- 3Read the lusterHold the specimen under a strong light. Luster: metallic.
- 4Match the color rangeCompare against the expected color range: gray, dark gray.
- 5Look at form & habitCrystal system: cubic. Typical habit: anhedral grains, nuggets, rounded inclusions in chromite.
Often confused with
Isoferroplatinum vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Isoferroplatinum leaves grayish-black, Native Platinum leaves grayish white.
How to tell apart: Sperrylite is the harder of the two (Mohs 6-7 vs. 5); streak differs, so Isoferroplatinum leaves grayish-black, Sperrylite leaves black.
Often found alongside isoferroplatinum
Minerals reported to co-occur with isoferroplatinum. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pt₃Fe
- Mohs hardness
- 5
- Density
- 16.5 g/cm³
- Streak
- Grayish-black
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Anhedral grains, nuggets, rounded inclusions in chromite
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Scientific reference
- Host rock
- In Pt–Fe and Cu–Ni sulfide deposits in ultramafic rocks, also in chromatites, and placers derived from them
Where rockhounds find isoferroplatinum
Classic worldwide localities
- Stillwater complex, Montana, and at Fox Gulch, Goodnews Bay, Alaska, USA
- Tulameen (type locality) and Similkameen Rivers, British Columbia, Canada
- Department of Chocó, Cauca, Colombia
- Inagli and Konder massifs, Aldan Shield, Sakha, Russia
- Noril’sk region, western Siberia, Russia
- Gusevogorskii pluton and the Kytlym and Uktus complexes, Ural Mountains, Russia
Field-hunting tip
Where it forms: In Pt–Fe and Cu–Ni sulfide deposits in ultramafic rocks, also in chromatites, and placers derived from them. If you start seeing platinum, iridium, osmium in float, you are in the right ground. Typical habit: anhedral grains, nuggets, rounded inclusions in chromite. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify isoferroplatinum?+
Where is isoferroplatinum found?+
What rocks look like isoferroplatinum?+
What minerals are found with isoferroplatinum?+
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Find isoferroplatinum on the map
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