Although many persons are content to collect gemstones in their own right (just as others collect coins or stamps or other collectibles), most gem lovers like to have their gems set in jewelry so they can be worn on the person. Unfortunately, despite the familiar refrain, diamonds, and other stones, are not necessarily forever. Most stones are more or less brittle, many are quite soft, and some can be damaged by heat, vibration, or chemicals. It's too bad that most jewelers do not educate their customers about how to care for their prized possessions. Here are a few tips.
 

• Stones that have a Mohs hardness of less than 8 are highly subject to scratching; harder stones are less likely to be scratched but are still subject to chipping and fracture. Remember that quartz, with a hardness of 7, is one of the most abundant minerals on earth, in the form of sand, or silica. When removing dust from soft stones, it's usually best to rinse them with clean water and dry with a soft cloth. Also, store jewelry and loose gems in separate padded compartments or wrapped in soft lint free cloth to prevent scratching, chipping, and entanglement.
   

• When cleaning nonporous gemstones, washing gently with a weak solution of ammonia, rinsing with clean lukewarm water, and drying with a soft lint free cloth is quite effective and safe. Just be sure to plug the sink so you don't wash your stones down the drain! On stones harder than quartz (Moh's hardness of 7), it's safe to do a little gentle scrubbing with a soft toothbrush, but if you're cleaning jewelry, be careful not to scrub highly polished metal surfaces, as the slight abrasive action of the brush will produce slightly hazy effects on the metal. A little soaking may be necessary to remove heavier deposits.
   

• If you use hand lotions or creams, remove your rings before applying them! This will help prevent heavy buildup of dirt and oil around your gemstones.
   

• If you plan to do heavy or dirty work with your hands, remove your rings so they will not be subjected to harsh blows, abrasives, or unnecessary dirt. Even diamonds are relatively brittle and can be chipped by a hard blow.
   

• Pearls, coral, and porous stones such as opal, turquoise, or malachite should be kept away from dirty water and oils to avoid discoloration. Wipe them gently with a soft, damp cloth. Do not wear rings containing these stones while washing dishes or similar activities.
   

• Be cautious about the use of ultrasonic cleaners. Some stones are subject to internal stress -- tanzanite, opal, emerald, organic gems (such as pearl, coral, and amber), turquoise, lapis, and malachite, any stone containing major inclusions, and most collector gems should not be exposed to ultrasound. Tanzanite has been known to shatter and opals to craze under ultrasound. Most emeralds and many rubies are "oiled" or resin-impregnated, and ultrasound may remove the treatment or expand existing fractures. If you are not absolutely SURE it's safe, don't put your stones in ultrasound!
   

• Diamonds are remarkably resistant to heat, but large stones and those with major inclusions are sometimes damaged by jewelers who linger too long with a torch during prong work. I've seen several stones that required repolishing after a benchworker allowed a torch to linger too long, especially when retipping platinum prongs (because of platinum's high melting point). It's often safest to remove them before working on a setting. Other stones are less resistant to heat and should never be exposed to extreme heat or sudden changes in temperature.
   

• Opal, pearls, coral, amber, turquoise, and many collector gems are quite heat sensitive (both to extremes and to sudden changes in temperature). Do not leave them sitting in hot sunlight, near radiators, or in hot cars. Once an opal begins to craze, it's usually unsalvageable.
   

• Brittle and soft stones should not be used in jewelry subject to hard wear, such as rings that are worn constantly. They are much safer in earrings, pins, pendants, or perhaps bracelets. They can be used in rings that are worn occasionally, such as dinner rings, but the setting should be designed to protect the stone as much as possible. Even though opals are popular in rings, it is a very hazardous use for them.
   

• If one prong of a four-prong setting breaks, it often results in the loss of a stone. Six prong settings are more secure. If a prong is weak or broken, it's usually best to replace the head than to attempt retouching prongs.
   

• Sharp corners, such as the tips of pearshapes and marquise cut stones, are especially susceptible to breakage and should be protected by the setting. Also, faceted stones with shallow crown angles (30 degrees or less), and thin or uneven girdles are particularly prone to chipping and need extra protection.
   

• Bezel settings offer more protection to stones, but they make it more difficult to remove and reset stones if the stone needs repolishing or if alterations of the metalwork are required. Setting can also be hazardous. It's best to use high-karat gold, which is softer and more easily bent into place. Also, consider how the stone might be removed if necessary. Sometimes, it may be best to use a false bezel setting and set the stone from beneath, holding it in place with tabs.