Raw platinum refers to the metal in its natural, unrefined state as it occurs within the Earth. It is found as elemental platinum or as natural alloys with other platinum-group metals and iron. This form contrasts with the highly processed, polished platinum commonly seen in jewelry or industrial applications. Understanding its appearance involves recognizing its distinct color, texture, and physical properties.
The Distinctive Appearance of Raw Platinum
Raw platinum presents a silvery-white to grayish-white color, often appearing slightly lighter than its refined counterpart. It can also exhibit shades ranging from tin-white to steel-gray or even dark gray, depending on its composition and impurities. The luster of raw platinum is metallic, though it appears duller compared to the bright sheen of polished platinum.
The texture of raw platinum is rough and irregular, commonly found in granular or crystalline forms. It can also occur as flaky or dendritic structures, while specimens found in alluvial deposits are waterworn nuggets with smoothed, rounded edges. Raw platinum is exceptionally dense, a property immediately noticeable when held. Pure platinum has a density of 21.45 grams per cubic centimeter, and natural specimens, due to other metals, range from 14 to 19 grams per cubic centimeter. This high density makes even small pieces feel remarkably heavy.
Raw platinum is known for its malleability and ductility, meaning it can be hammered into thin sheets or drawn into fine wires, even in its natural state. Its hardness measures between 4 and 4.5 on the Mohs scale. While well-formed crystals are uncommon, raw platinum can be found as distorted cubic crystals with rounded corners. More often, it is encountered as small, irregular nuggets, grains, or flakes.
Natural Occurrence and Forms
Raw platinum is found in Earth’s crust in two main types of geological settings: placer deposits and lode deposits. Placer deposits, the most common source, consist of loose grains or nuggets weathered out of their original rock formations and transported by water, often accumulating in riverbeds or ancient streambeds. These deposits form because platinum’s high density causes it to settle and concentrate in areas where water flow decreases, such as behind obstacles or in river bends.
Lode deposits involve raw platinum still embedded within its host rock. These primary occurrences are found within ultramafic igneous rocks, which originate deep within the Earth’s crust. In these environments, platinum coexists with other minerals, including various sulfides of nickel and copper.
The size of raw platinum pieces found in nature can vary significantly, from microscopic grains and flakes to larger nuggets. While most pieces are small, rare lumps weighing up to 30 kilograms have been reported. The presence of associated minerals often influences the overall appearance of raw platinum, as it may be intergrown with or surrounded by these other geological materials.
Distinguishing Raw Platinum from Similar Materials
Identifying raw platinum requires careful observation of its unique physical and chemical characteristics, as it can be confused with other metals like silver or lead. Platinum’s color is a grayish-white, which differs from the brighter, more reflective appearance of newly polished silver. Unlike silver, which tarnishes, platinum is highly resistant to corrosion and does not tarnish.
A defining feature of raw platinum is its exceptional density, making it feel notably heavier than visually similar metals of the same size. Its density is significantly higher than silver or lead. This weight difference is a practical cue for identification. While pure platinum is non-magnetic, some natural specimens may exhibit a slight magnetic attraction due to common iron impurities. This contrasts with steel, which is strongly magnetic.
Raw platinum possesses a greater hardness (4-4.5 on the Mohs scale) compared to softer metals like silver or lead, meaning it is more resistant to scratching and deformation. Chemically, platinum stands out due to its high resistance to most acids; it only dissolves in a mixture called aqua regia, unlike many other metals that react with common acids. This chemical stability contributes to its enduring nature in various environments.