In the field of economics, the laws of supply and demand state that the price of a product and its available supply to the market are interconnected. For example, if a good such as crude oil is produced in excess, the price will drop accordingly.
However, sometimes substances are nearly impossible to produce in the first place—and that means that it can be extremely difficult for the market to respond to increases in demand. The world’s most valuable substances generally fall into this category and this makes their value per gram very high.
White truffles, for instance, only grow for a couple of months of the year, almost exclusively in one part of Italy. They must be foraged by special pigs, and they seem to be worth more every year. The price per gram for white truffles is $5, which means that a pound costs close to $2,000.
Despite this, white truffles barely crack the list of the most valuable substances by weight.
Saffron, a spice that is gathered from the flower of the crocus sativus plant, is another notch higher on the list. To get one pound of dry saffron requires the harvest of 50,000 to 75,000 flowers. There’s only 300 tonnes of production each year, and that annual production is worth around $3 billion.
Higher up on the list of the world’s most valuable substances are some familiar metals. Silver does not make the list, as it is only worth around $0.50 per gram. However, many of the platinum group metals (PGMs) do make the list: platinum, palladium, rhodium and iridium all range between $16 and $27 per gram. Gold also makes the list, and it has traded for more than an ounce of platinum since early 2015. One gram of gold is worth just under $34.
At the top of the list we find a combination of extremely rare metals, radioactive isotopes and gemstones.
The radioactive element californium, first made in 1950, is the most valuable at $27 million per gram. It is one of the few transuranium elements that have practical applications, being used in microscopic amounts for metal detectors and in identifying oil and water layers in oil wells.
Diamonds are near the top of the list as well at $65,000 per gram, though like many other gemstones, the value depends on the specific crystal in question. Many industrial diamonds are relatively cheap, but the rarest and most beautiful stones can be worth millions.
Iranian beluga caviar and crème de la mer are the most expensive non-metals or non-gemstones on the list. Iranian caviar is made from the roe of beluga sturgeons found in the Caspian Sea, and it is valued at about $35 per gram. Crème de la mer was originally created by a physicist for NASA to heal his burns, but it is now sold as a face cream by Estée Lauder for $70 per gram.