Platinum is a native metallic mineral, formula Pt. Natural grains often contain iron, iridium, osmium, or other platinum-group metals, so a field grain may not be pure platinum.
It is dense, malleable, and silvery gray, with a Mohs hardness of about 4 to 4.5. Crystals are isometric but rare. Most platinum is found as small grains or nuggets in ultramafic rocks and in placers derived from them. It does not tarnish easily, which helps separate it from many look-alike metallic grains.
This page is only for platinum. Iridium, osmium, and palladium are related metals, not this mineral.