Pearl is one of the three birthstones for June (the other June birthstones are alexandrite and moonstone). Pearls are organic gems grown in saltwater or freshwater oysters or mussels in oceans, lakes and rivers around the world. Pearls form when the mollusk secretes a substance called nacre around an irritant such as a piece of sand  has invaded its shell.

Pearls formed naturally are very rare and almost all pearls sold today are cultured pearls raised on pearl farms. Technicians implant a piece of mantle tissue alone (common for freshwater cultured pearls) or with a mother-of-pearl shell bead (all saltwater) into a host mollusk. The mollusk covers the irritant with nacre, just like a natural pearl. The mollusks are cleaned, protected from predators and eventually harvested. 

Saltwater cultured pearls are grown in many areas around the world. Akoya cultured saltwater pearl farms are primarily found in Japan and China. South Sea cultured pearls are farmed from the northern coast of Australia through Indonesia to the southern coast of Southeast Asia, with large operations in the Philippines as well. The Gambier Islands and the Tuamotu Archipelago, both part of French Polynesia, are two locales where the rich black Tahitian pearls are cultured. Pyramid Studios has a large selection of lustrous, dusky and iridescent Cook Island Pearls.The Cook Islands are in the South Pacific Ocean, northeast of New Zealand, between French Polynesia and American Samoa. China is the dominant source of freshwater cultured pearls.

Pearls are valued for qualities including size, shape, color, luster, surface quality, nacre quality, and—for jewelry with two or more pearls—matching. Luster gives a pearl its beauty and we feel it is the most important quality factor. When you look into a pearl, you see a reflection and the brighter and sharper that reflection is, the more lustrous the pearl.

Nacre, also known as mother-of-pearl, is a crystalline substance that creates the iridescent visual effect of the pearl. It is an organic substance secreted by mollusks over an intruding irritant or implanted nucleus. It is a strong and resilient material that is lightweight and transparent, allowing light to transmit and refract light rays through crystalline layers that act as tiny prisms, breaking up the beam and refracting back color creating the pearl's shine and iridescence. 

Ideally, the pearl's surface should be as free of  bumps, spots, discolorations, or other disfiguring characteristics as possible. A smooth and clean surface is more highly valued. 

Perfectly round pearls are extremely rare and very difficult to culture, and therefore are rare and expensive. However, pearls come in a wide variety of interesting and unique shapes, and you may fund that a lustrous pearl in a different shape is highly desirable. Button pearls are slightly flattened into a disk-like "button" shape; drop pearls are teardrop-shaped; ringed pearls exhibit a series of concentric indentations or rings; and baroque pearls are abstract and asymmetrical. Many high-quality pearls can be found in these alternate shapes often at lower prices than a perfectly round pearl of the same quality and you may find the unique shape to be even more personally appealing and satisfying.      

The size of the pearl is measured by its diameter in millimeters. Akoya pearls tend to be in the 6-8 millimeter range, while South Sea  and Tahitian pearls tend to be larger. Freshwater pearls are available in a wide variety of different sizes. With all other qualities equal, larger pearls are priced higher. 

Pearl color can have three components. Bodycolor is the pearl’s dominant overall color. Overtone is one or more translucent colors that lie over a pearl’s bodycolor. And orient is a shimmer of iridescent rainbow colors on or just below a pearl’s surface. All pearls display bodycolor, but only some show overtone, orient, or both. Pearls occur in a wide variety of colors depending on the mollusk in which they grow. The most familiar are white and cream, but the palette of colors extends to every hue.