Why is it that pearls are perfectly round? Does it always happen that way?
Pearls are not perfectly round. Every pearl contains some imperfection.
From what I have read, nearly round pearls are relatively rare, making
them more valuable. They are graded according to shape, size, and color.
I saw a very interesting article on pearls in a recent National Geographic
(probably one of the 1993 issues) if you want to research this topic
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Update: June 2012