Diamonds are among the hardest of all minerals. Still, they require special care to keep them looking their absolute best.

The brilliance of any diamond depends on the amount of light that can enter the stone and reflect back to the human eye. However, the smallest deposit of grease on the surface of a stone can dull its reflection. Even a touch from a finger will leave a smudge of natural oil, according to De Beers, one of the world's leading diamond companies.

Clean your diamonds with a simple mix of six parts water to one part ammonia and apply with a soft, natural bristle brush. If you have no ammonia in the house, you can substitute with a mild liquid detergent. Rinse with fresh water and dry with a soft, non-abrasive cloth. If your diamond has a crack or inclusion, De Beers advises owners not to use ultrasonic cleaners, as the vibrations of the cleaners can enlarge flaws.

A few words of warning. De Beers recommends that jewelry not be cleaned in or near the sink. If there is no better location for the cleaning, be sure the plug is in, to avoid the jewelry going down the drain. If you are using a brush, be gentle: diamonds can work loose from their settings if treated roughly, warns De Beers. If you use hand lotion, wait for at least 10-15 minutes before putting your rings back on, as the ring might easily slip off.

While most people believe that diamonds are impervious to scratches, that simply is not the case. Indeed, another diamond can easily scratch another. To prevent such scratches, separate diamond jewelry in your jewelry box, advises De Beers. Diamonds also can scratch other gems or jewelry, especially soft items like pearls. And even though diamonds are hard, they can be brittle, especially along thin edges. Try not to wear your diamond when it might be struck sharply, and if you have an especially thin cut, keep it protected. If you are traveling, use a secure travel pouch, which will keep individual pieces safely apart, according to De Beers.

De Beers recommends having important pieces of jewelry checked quarterly to be sure the stones are secure in their settings.