Pearls are sought-after gems from the ocean

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"Have any gems been found in the ocean?" asked a young Cook Memorial Public Library patron while attending "Tween" Science Explorers at the Libertyville library.

Gems can be found almost anywhere.

Chicago's Field Museum of Natural History's Gems and Minerals Collection describes gems as "minerals that are cut, polished and used for adornment."

Most often gems are hidden deep inside the earth, but there are places on the earth's surface where gems can be uncovered.

With a shovel, an $8 admission ticket and a little luck, you can locate a few diamonds glinting on the surface of a plowed 37-acre field at Arkansas' Crater of Diamonds State Park. Diamonds are unearthed almost daily at the state park, which has a "finders, keepers" policy.

Sought-after gems from the ocean are pearls, mother-of-pearl, abalone and coral. Along with amber, these are called organic gems because they are created by living organisms and become mineralized.

"It is truly amazing to realize that a pearl's formation starts as an irritant inside a mollusk, and over a long period of nurturing, out comes a uniform, lustrous, iridescent gem," said Sam Chau, an accredited jewelry professional at TC Jewelry in Vernon Hills. "It's this unique iridescence that makes it so valuable and treasured all over the world."

Pearl-bearing mollusks are found in fresh water and in oceans. Sand enters the mollusk shell and irritates the animal, which responds by covering the sand with nacre, resulting in the formation of a lustrous pearl.

Pearls come in a variety of colors such as white, gray, pink, black, bronze, blue, blue green, yellow and violet.

Pearls can be man-made. The process can take two to three years to yield a round, shiny gem. Pearl farmers insert an irritant into an oyster shell that triggers the process in which the pearl is constructed with nacre. Chau said some man-made pearl necklaces are extremely valuable.

"A graduated strand of blemish-free 12mm to 16mm Tahitian pearls can cost $75,000," he said.