The rarest precious metal is generally considered to be Rhodium. It is a silvery-white metal that is a member of the platinum group of metals, and it is estimated that the annual production of rhodium is only around 30-40 tons per year. This is significantly less than other precious metals like gold, silver, and platinum.

Rhodium is highly valued for its unique properties, including its high melting point, resistance to corrosion and wear, and its ability to act as a catalyst in chemical reactions. It is often used in industrial applications such as catalytic converters in cars, where it helps to reduce emissions.

Due to its rarity and high demand in industrial applications, the price of rhodium can be quite volatile and has fluctuated significantly in recent years. In fact, in early 2020, the price of rhodium surged to its highest level in more than a decade. This high value makes rhodium a valuable and sought-after precious metal.