The term "diamonds are a girl's best friend" was popularized by the song of the same name from the 1949 musical Gentlemen Prefer Blondes. The song is sung by the character Lorelei Lee, who is extolling the virtues of diamonds as gifts for women.
The scarcity of diamonds is controlled by the supply and demand in the market. While there are a limited number of diamonds that can be mined, they are not necessarily rare. The price of diamonds is determined by how much people are willing to pay for them.
The largest suppliers of diamonds in the world are De Beers and Rio Tinto. They maintain their dominance in the market by controlling a large share of the world's diamond production and by marketing diamonds as a rare and precious commodity.
Diamonds are mined in a number of ways, depending on the type of deposit. For example, alluvial deposits (which are found in riverbeds) are mined using sieves and other methods to extract the diamonds from the sediment. Hard rock deposits are mined using explosives and heavy machinery to break up the rock and then extract the diamonds.
Whether or not it is ethical to mine diamonds depends on a number of factors, including the working conditions of miners, environmental impact of the mining operations, and whether or not the diamonds are conflict diamonds (i.e. used to finance wars or other violence).
The world's most expensive diamond is the Pink Star, which was sold for $71.2 million at a Sotheby's auction in Geneva in 2013.
Before diamonds became popular, other gemstones such as sapphires, emeralds, and rubies were commonly used in engagement rings. However, the popularity of diamonds began to increase in the 1940s, and by the 1950s, they had become the most popular choice for engagement rings. Today, an estimated 80% of engagement rings include diamonds.