In terms of material elemental rarity, gold wins hands down. Diamonds are made up of carbon atoms- which are not inherently rare as an element, because you can find them everywhere- even in your own body.
Why is it thought that based on weight, gem-quality diamonds are much more expensive to buy today? Well, aside from the various quality factors that create a value-hierarchy in the diamond trade, this gemstone species has to go through a lot of rare environmental conditions to manifest.
What makes diamonds truly rare, is the specific manner in which they form or crystallize. Highly pressurized carbon (under the correct ratio of temperature) can turn into diamond. Without this extreme pressure, another material may form instead. You know this as graphite, which is so very dark and soft that artists use it to create drawings and portraits.
While diamonds can only form deep below, in the earth's mantle regions, the geological journey that brings them to the surface can also sometimes destroy them. An imbalance of heat and pressure for prolonged periods of time can graphitize the carbon mass in diamond.
Because of this, only a (relative percentage) few transparent, fine crystals of diamond ever make their way up to an extractable level for miners to acquire it. There are a lot more low-quality diamonds out there though that people can still mine for use as abrasive material, but these aren't counted in our comparison because their prices are very different from gem-quality samples.
Today though, there is a great amount of concern in the diamond industry. While rare conditions create natural diamond deep beneath the earth's surface, man can now replicate those conditions in a lab. This technology- once proprietary in the ownership of a view, is spreading so that many companies around the world can now 'create diamond'. Chemically equivalent in its composition and structure, man-made diamond has finally gotten to the point that normal vision cannot always separate it from its natural counterpart.
Advanced gemological instruments that make use of spectrometric data, can separate the two kinds of diamond, but not everyone has access to these machines. This begs the question- are diamonds still rare? Many people are on opposing sides of the debate. Natural earth-mined diamonds cannot be created, because by definition they are products of nature. Man-made diamonds will only grow in potential quantity over the next decades, due to the propagation of technology. It's really up to you to decide where you stand on the matter.
Man-made versions of rubies and sapphires have existed since the 1800's, but while they are very cheap today, they haven't really affected the values of natural rubies and sapphires in the long run of history.
Gold is finite here on earth, the reserves can't be man-made or replicated, from what we know. It's an element, and there is a specific amount of it that has yet to be extracted from the earth's soil. Once that's dug out, what then?
Natural diamonds are very rare and expensive. Gold as an element or material is more rare, but currently less expensive. The question of rarity does not have a cut-and-dry answer, but we hope that this article has shed a bit of insight on the matter.
