Gems and precious metals are gifts of nature, which need special care. Even though a gem may be millions of years old, once mined and worn, it is exposed to conditions and chemicals that can damage it.

The harder the gem, the less vulnerable it is to potential damage. A diamond, for example, is the hardest gem known to man, and that's one reason why "it is forever."

Hardness is based on a gem-trade standard called the Mohs Scale, developed in the early 19th century. The scale is structured so that material rated at each higher number can scratch substances with lower numbers. Diamonds are rated the highest, at 10; rubies and sapphires are Mohs 9; emeralds and topaz, 8; and garnets, tourmalines and quartz, 7. Anything softer than a 7 can be scratched, including opal, turquoise, lapis lazuli, coral, pearl.

Gold, silver, and platinum are only Mohs 2-1/2 to 4, which means that they require special care when wearing, storing, or cleaning.

Here are some Do's and Don'ts:

DON'T wear fine jewelry when doing housework or gardening.

DON'T heap your jewelry into one drawer. Remember a diamond ring can scratch that pearl necklace. Keep them separate and ideally wrapped in velvet, paper, or silk.

DO check for loose stones frequently by gently tapping the piece with your finger near your ear.

DO get pearls restrung every two years or annually with frequent use.

DO clean fine jewelry often to maintain its sparkle and beauty. Do not use toothpaste as its abrasives can damage softer gems and metals. All fine jewelry can be safely cleaned by soaking for 10 minutes in warm soapy water (using a non-detergent soap). Use a soft brush on harder gems to loosen any dirt around the prongs. To reduce greasy build-up on diamond jewelry, dip it in plain alcohol or vodka before soaking.