Yes, peanut butter can be made into diamonds, but people shouldn't buy out the nut butter shelf at their local market just yet. In order to make one into the other, conditions of intense pressure and very high temperatures are needed, and most people don't have access to such conditions. Using sophisticated scientific equipment, however, it is possible to make peanut butter into diamonds; the same principle can be used to turn a wide variety of things into diamonds, in fact, as the stones are simply a form of carbon.

A diamond engagement ring.

Natural diamonds are created through a process that takes millions of years. Conditions for their creation are found deep inside the Earth's crust, where temperatures are very high and pressure can get quite intense. Over millennia, carbon is compressed into the form of a diamond. Materials at meteor impact sites can also be made into diamonds, as a result of sudden high heat and pressure, although the resulting stones are typically very small.

A jar of peanut butter.

When these gems are made from peanut butter (and other substances), the substance is subjected to very high pressure while being heated. One way to create the necessary pressure involves squeezing a sample between two diamonds; since this stone is one of the hardest substances on Earth, this technique can yield incredibly high pressure measurements. When the material is also heated to around 2,000°F (1,093°C), it can turn into a diamond.

The resulting gem, however, is not much to look at. Most peanut butter diamonds are quite small, around the size of a fennel seed, and they are also discolored, due to impurities in the peanut butter. These discolorations are rarely strong enough to classify the stone as a fancy diamond; instead, it just looks muddy. When peanut butter is made into a gem, the goal is usually novelty rather than a stone that could be sold on the open market.

Synthetic diamonds can be made from a wide variety of materials, and many of those other materials are more for the purpose than peanut butter. In fact, synthetic gems have reached a point of such high quality that it can be difficult to tell that they are “fakes,” as they are chemically identical to the real things. Most fancy diamonds on the market, for example, are synthetic, or they are made from natural stones that have been irradiated to produce the desired color.

The process that is used when peanut butter is made into diamonds can also be used for ashes. Several companies around the world will make memorial gems from the ashes of loved ones and pets. If an individual is particularly attached to a jar of peanut butter, he could probably make the necessary arrangements for a gem-quality peanut butter diamond, but he should be prepared to pay a hefty price; even the smallest of such gems typically costs thousands of US Dollars.