wholesale diamonds is the hardest of all gemstones; it is the simplest in composition; it is ordinary carbon. Colossal heat and pressure, over the eons, crystallized the diamond dealers into what it is today.
diamond fashion in jewelry are the most popular of all gemstones. Their price and rarity is carefully monitored by the major diamond cartels. As a result the price of diamond dealers in jewelry is pretty well standardized to size and quality of the stone.
Most gold engagement ring were formed more than 100 miles below the surface of the Earth, some from perhaps 400 miles down.