What makes “precious” metals so precious?
Gold, silver, or platinum are usually considered THE precious metals. Gold has been known and highly valued from earliest times, not only because of its beauty and resistance to corrosion, but also because gold is easier to work than all other metals. In addition, gold was easier to obtain in pure form than the other metals. Because of its relative rarity, gold became used as currency and as a basis for international monetary transactions. The unit used in weighing gold is the troy ounce; 1 troy ounce is equivalent to 31.1 grams. Silver, with the exception of gold, silver is the most malleable and ductile of all metals. It is harder than gold but softer than copper. Silver melts at about 962°C, boils at about 2162°C. Platinum, because of its chemical inertness and high fusing point, platinum is valuable for laboratory apparatus, such as crucibles, tongs, funnels, combustion boats, and evaporating dishes. Small amounts of iridium are usually added to increase its hardness and durability
