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Pearl
| Chemical Formula | CaCO3 |
| Mohs Hardness | 3 |
| Specific gravity | 2.7 |
| Description | A peral is a hard object produced within the soft tissueof a living shelled mollusk. Just like the shell of a clam, and is composed of calcium carbonate in minute crystalline form, which has been deposited in concentric layers. Pearls are formed inside the shell of certain mollusks as a defense mechanism against a potentially threatening irritant such as a parasite inside the shell, or an attack from outside that injures the mantle tissue. The mollusk creates a pearl sac to seal off the irritation. Because pearls are made primarily of calcium carbonate, they can be dissolved in vinegar. Calcium carbonate is susceptible to even a weak acid solution because the crystals of calcium carbonate react with the acetic acid in the vinegar to form calcium acetate and carbon dioxide. |
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