While many diamonds are sold loose, as a precious commodity on diamond exchanges, nothing may equal them when set in jewelry. No engagement ring would be worth the name, unless containing a diamond, which, appropriately enough was considered in a successful advertising company the gem that lasts 'forever'. And no cubic zirconium or whatever other stones resembling a diamond could ever replace it.
So what is so unique about this gemstone? While it is both incredibly old and hard, what makes it unique is its luster, namely its quality of dispersing the white light into all the colors of the spectrum. No other precious stone could do this, and the diamond can because of its unequaled purity. While it is true that there are many diamonds that are not a hundred percent pure or transparent, a thing reflected in their color - blue, yellow, green, red, brown, pink, purple, orange or even black, it's as true that people consider the genuine stones to be colorless, or rather of all colors at the same time, thanks to their miraculous quality of dispersing the light. After all, color, carat and clarity are, besides the cut, the properties that distinguish them from one another. And you'll never see any royal jewelry without white diamonds.
But given the pace at which diamonds are being extracted nowadays, almost half coming from central and southern Africa (26,000 kg a year), of course, everyone can afford to have at least one piece of jewelry with diamonds set in, besides the traditional engagement ring for women.
The way in which they disperse the light makes them look much bigger than they actually are; therefore, some small studs or cuff links could draw the attention of a whole room, especially if strongly artificially lit. This makes diamond jewelry priceless for being worn on formal occasions, such as at formal dinners, at the opera or theater, at balls or any other formal gatherings. On the other hand, less conspicuous diamonds, such as the black ones would make elegant and classy jewelry for business suits, especially if set in platinum or white gold. Without the dazzling reflection of light, they may also afford to be bigger. As fit for corporate clothing could be brown diamonds, which would look besides as beautiful, if set in yellow gold.
If diamonds, in general, wouldn't look utterly gorgeous, they wouldn't sell for as much as 24 million dollars one piece, like the blue diamond once owned by the King of Spain, and neither would they total, in terms of wholesale jewelry, 28 billion dollars a year (as far back as 2002).