Physical features
1. Color- White to greenish-blue, pink and black.
2. Streak- White.
3. Luster- Pearly.
4. Cleavage- None.
5. Transparency- Translucent.
6. Fracture- Breaks uneven.
7. Hardness- 3.5 to 4.
8. Forms- Oval.
Pearls form inside any living mollusks. Most commonly grown in oysters but also occur in conchs, clams and even mussels. Mollusks live in both subtropical and tropical waters. Pearls form when a particle of sand, or by any other irritant that gets trapped between the shell and the soft outer body parts of the mollusk. In order for the mollusk to ease the irritation it secretes narc. Some pearls may even form a cyst due to encystation, and as the narc continues to secrete around the irritated area, layers begin to build, and after about 7 years a pearl will form. Freshwater pearls are fished out of rivers in Europe and the U.S.A. These pearls (shown above) are from Asia.
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