File:Platinum nuggets (placer platinum) (Granite Creek, southern British Columbia, Canada) (17125947987).jpg

Platinum nuggets from Canada. (each is ~1 to 2 mm in size)

A mineral is a naturally-occurring, solid, inorganic, crystalline substrance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 4900 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.

Elements are fundamental substances of matter - matter that is composed of the same types of atoms. At present, 118 elements are known (four of them are still unnamed). Of these, 98 occur naturally on Earth (hydrogen to californium). Most of these occur in rocks & minerals, although some occur in very small, trace amounts. Only some elements occur in their native elemental state as minerals.

To find a native element in nature, it must be relatively non-reactive and there must be some concentration process. Metallic, semimetallic (metalloid), and nonmetallic elements are known in their native state as minerals.

Platinum (Pt) is far more valuable that gold, but it doesn't have a distinctive, prestigious color. Like most metals, platinum has a silvery color. Platinum, when purified, is heavier than gold, but specimen platinum has about the same specific gravity as gold nuggets (about 19).

Platinum is alway found significantly alloyed with other elements, usually other PGEs (platinum-group elements: platinum (Pt), palladium (Pd), osmium (Os), iridium (Ir), rhenium (Re), rhodium (Rh), ruthenium (Ru)). Platinum is typically found in Precambrian ultramafic igneous rocks, but there are also some Pt-bearing placer deposits in Canada, Colombia, and Russia.

The small platinum nuggets shown above are from a placer deposit in Granite Creek, a tributary of the Tulameen River near Granite City, a ghost town in southern British Columbia, Canada. This was a significant platinum occurrence. It's been reported that >20,000 ounces worth of platinum nuggets were recovered from this area from the mid-1880s to the mid-1930s. Granite Creek platinum nuggets are derived from weathering of PGE-bearing chromitic dunites in the Tulameen Ultramafic Complex of Early Jurassic age.

Available assay information indicates that Granite Creek nuggets are 68 to 78% platinum (Pt), 4 to 14% osmiridium (Ir,Os), 8 to 10% iron (Fe), 3 to 4% copper (Cu), 3% rhodium (Rh), 1% iridium (Ir), and 0.2% palladium (Pd).