Pearls—What’s the Difference?
The pearls on your necklace are real, but are they naturally made? Probably not.
Most pearls sold today are cultured, with the rarity of natural pearls to blame. However, the milky, shimmering wonders aren’t any less coveted because of their formation method. They’re viewed as a classic piece that goes with a multitude of clothing ensembles and jewelry types.
Pearls form when mollusks defend themselves against predators that enter their shells. The predator becomes trapped in the membrane between the mollusk’s shell and mantle, and the mollusk coats the predator with a substance called nacre. After a period of time, it forms a pearl.
The smooth, round, white pearl that usually comes to mind isn’t the only type mollusks make. Several beautiful varieties exist, all with distinguishable characteristics.
 
Natural vs. Cultured
Natural pearls remain as ones that form in mollusks without any interference from mankind. Though most are thought to have been harvested in the early days, natural pearls can still exist, but they are typically more expensive. A natural pearl may be one you find out of the blue on the beach.
A cultured pearl, on the other hand, stands as one whose formation has been initiated by sticking an irritant, usually a bead, into the mollusk to trigger the defense mechanism. Workers place the mollusks into the water to care for them during the process. As the mollusk adds coats of nacre onto the bead, a pearl eventually forms. Yet the pearl isn’t always good enough to use; sometimes thousands of pearls need to be harvested just to find enough to make one necklace.  
 
Though natural pearls are rare, you may find one while walking along the beach.

Saltwater vs. Freshwater
Saltwater and freshwater pearls differ in the obvious way that the former developed in salt water while the latter in fresh water, like rivers and lakes. While saltwater pearls tend to be round, freshwater pearls come in several shapes. Both boast a spectrum of colors as well as sizes. Three of the most popular pearls, Tahitian, Akoya and South Sea, are saltwater pearls.
 

Akoya Pearl: Most Akoya pearls are produced in Japan in salt water and resemble a classic pearl, sporting a round shape, white color and smooth surface. The Akoya oyster remains the tiniest currently used for making pearls, so the pearls usually come in smaller sizes. The Akoya pearl is what most picture when thinking of a pearl.   

 

Tahitian Pearl: The Tahitian pearl comes from salt water and is often known as the black pearl. However, not all Tahitian pearls are black; many reflect silver or gunmetal while others are iridescent. They’re usually round, yet some can be slightly asymmetrical in shape. The pinctada maxima oyster composes larger pearls, but its sensitivity drives the cost of Tahitian pearls, which can be difficult and expensive to make.    

 

South Sea Pearl: South Sea pearls hail from the body of water between Australia and China, and currently stand as some of the largest pearls commercially produced. The pearl usually gleams in white, gold or silver as well as sports a satin-like luster.   

 
Other Pearl Elements: Several pearl-related jewelry components stem from pearl creation. When a mollusk rejects a pearl, fragments of what was to be remain small, baroque-shaped pearls called keshi. Mollusks secrete nacre, which builds up on the inner sides of its shell to form mother of pearl, a substance of which jewelry can be made as well.