Re:  Allseller888's pearl tips, I would never light pearls on fire to see if they're real.  Unless you have a strand that you don't mind losing.  Rubbing pearls together to see if there is friction is one way, but the best way is to scrape your teeth over them and if there is a gritty feeling, then they're real.  Fake pearls don't have this gritty sensation. 

Since the majority of real pearls sold today are "cultured", because of ocean pollution and the rarity of finding a non-cultured pearl, "cultured" pearls are almost as valuable.  China and Japan lead the pack in culturing pearls by inserting a bead or an object for a desired shape, and the oyster senses this as an irritant and as a defense, starts coating the irritant w/nacre, which is a shell-like substance, which several layers later becomes a pearl.  Colored cultured pearls, are oftentimes irradiated pearls and if looked at through a special viewer such as appraisers have, will reveal the true color (usually white) of the pearl.  These pearls are usually hardy, but should be substantially less costly than true white cultured pearls. However, some oysters produce colored pearls, usually in the pinkish to bluish shades, and sometimes grey.   Uneven sized pearls, such as the shape of a potato, are usually either cultured or real, non-cultured pearls.  These particular shaped pearls can also be cultured to look a certain shape, such as a baroque-style pearl, which are somewhat bumpy in shape, but nonetheless popular and appealing to certain buyers.

The markup of pearls is substantial and if one visits abroad, you can usually find beautiful, reasonably priced pearls at a fraction of the cost.  The huge price increase here in the US is not always an indicator of quality.  I have pearls I have bought from wholesalers and then mark-up for sale which are still considerably less expensive than the same pearls found in jewelry stores, mostly upper-end.  Caveat emptor (let the buyer beware).