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Pearl Care
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Which of the following is hardest and which is softest?
• A pearl
• An opal
• Pure gold
• A tooth

The hardest is the opal. It has a hardness of 5 1/2-6 1/2
on the Moh's scale, which rates the relative hardness of materials from 1 to 10. (The 10 rating of a diamond is the highest, but a diamond is over 1000 times harder than an opal.) Hardness is a material's resistance to scratching and abrasions.

The softest of the four materials above is pure gold, which has a hardness of 2-2 1/2. When alloyed with other metals, the hardness of gold increases, but it is still a relatively soft metal. Tooth enamel has a hardness of 5, and a pearl has a range of 2 1/2- 4. In other words, a pearl is a relatively soft material.

Knowing how soft a pearl is can help us understand why pearls should not be tossed on top of or next to other gems in a jewelry box. Knowing that a tooth is harder than a pearl helps us understand why the "tooth test" for dentifying imitations should only be done very lightly or else avoided. The basic concept of hardness is that a harder material will scratch one that is softer.

Besides being soft, pearls are easily damaged by chemicals or eaten away by acids such as vinegar and lemon juice. Heat can turn pearls brown or dry them out and make them crack.

One advantage of pearls is they are fairly tough considering their softness. In his book Pearls, Alexander Farn relates how jewelers and pearl merchants of oldwould separate imitation pearls from real ones by having footmen stomp on them. Those that were crushed were imitation. The natural pearls normally would resist such blows. Cultured pearls, especially those with thin nacre, are not this durable. Therefore, avoid dropping or crushing them.

Cleaning Your Pearls

The softness of pearls and their low resistance to heat and chemicals mean that special precautions must be taken when cleaning them. Keep in mind the following guidelines:

• Do not use commercial jewelry cleaners on pearls unless the labels say they are safe for pearls. Many of them contain ammonia, which will cause deterioration.

• Never clean pearls in an ultrasonic cleaner. It can damage the pearls and wash out the color if the pearls have been dyed.

• Never steam-clean pearls. Heat can harm them.

• Never use detergents, bleaches, powdered cleansers, baking soda or ammonia-based cleaners on pearls.

• Do not use toothbrushes, scouring pads or abrasive materials to clean pearls. They can scratch their surface. If there's a lump of dirt that can't be rubbed off with a soft cloth, try using your fingernails. They have a hardness of only 2 1/2 or less.

Cleaning pearls is not complicated. After you wear them, just wipe them off with a soft cloth or chamois which can be dry or damp. This will prevent the dirt from accumulating and keep perspiration, which is slightly acidic, from eating away at the pearl nacre.
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