A platinum nugget is a heavy, malleable, dense metallic mass typically found in alluvial placer deposits derived from ultramafic rock. Identify it by its silvery-white color and extreme heaviness relative to similarly sized rock such as magnetite. It is rarely found as a well-formed crystal, occurring mostly as a rounded water-worn grain or flattened nugget.
Is this platinum nugget?
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 platinum nugget with a known reference. Platinum Nugget sits at Mohs 4-4.5, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Platinum Nugget leaves a silvery-white streak.
- 3Read the lusterHold the specimen under a strong light. Platinum Nugget typically shows a metallic luster.
- 4Match the color rangeCompare against the expected color range: silvery-white, gray.
- 5Look at form & habitCrystal system: cubic. Typical habit: nuggets, grains, rarely cubic crystals.
Often confused with
Platinum Nugget vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Sperrylite is the harder of the two (Mohs 6-7 vs. 4-4.5); streak differs, so Platinum Nugget leaves silvery-white, Sperrylite leaves black.
How to tell apart: Streak differs, so Platinum Nugget leaves silvery-white, Palladium leaves silver-white.
How to tell apart: Platinum Nugget is noticeably harder (Mohs 4-4.5 vs. 2.5); streak differs, so Platinum Nugget leaves silvery-white, Galena leaves lead-gray.
Often found alongside platinum nugget
Minerals reported to co-occur with platinum nugget. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- Pt
- Mohs hardness
- 4-4.5
- Density
- 14-19 g/cm³
- Colors
- Streak
- Silvery-white
- Luster
- Metallic
- Transparency
- Opaque
- Crystal system
- Cubic
- Crystal habit
- Nuggets, Grains, Rarely Cubic Crystals
- Cleavage
- None
- Rarity
- Rare
- Uses
- Collector, Precious Metal, Industrial
- Host rock
- Ultramafic Igneous Rocks, Alluvial Placer Deposits
Where rockhounds find platinum nugget
1 mapped spotsClassic worldwide localities
- Ural Mountains, Russia
- Bushveld Complex, South Africa
- Choco, Colombia
- Stillwater Complex, USA
- Sudbury, Canada
Field-hunting tip
Look in ultramafic igneous rocks, alluvial placer deposits country, the host setting where platinum nugget typically forms. If you start seeing chromite, olivine, magnetite in float, you are in the right ground. Field specimens usually show a nuggets, grains, rarely cubic crystals habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in California. Start trip planning there.
Common questions
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Find platinum nugget on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
