Natural vs Cultured Pearls: What's the Difference?

Natural pearls and cultured pearls are grown the same way, by a living mollusk laying down layers of nacre. The difference is how the pearl starts. The table sums up the main differences.

How natural and cultured pearls form#

A natural pearl forms in the body, or the mantle tissue, of certain mollusks, usually around a microscopic irritant, and always without human help of any kind.⁷ A predator, a parasite or a lodged particle can move shell-making cells into the mollusk’s body, where they form a pearl sac and keep making nacre.²

A cultured pearl needs people to start it. A technician takes mantle tissue from a donor mollusk and inserts it into a host, either with a shell bead in the gonad or as pieces of tissue alone in the mantle. The tissue forms a sac and coats the bead or tissue with nacre.⁷ CIBJO defines cultured pearls as pearls formed inside living mollusks, in a cultured pearl sac, with human intervention.⁸ The page how pearls form explains both processes.

How rare natural pearls are#

Natural pearls are rare. Hundreds of pearl oysters or mussels must be gathered and opened to find even one, and perfectly spherical natural pearls are extremely rare and highly valuable. For centuries this was the only way to get pearls.²

The trade was once large. From 1850 to 1930, the Persian Gulf supplied perhaps 70–80% of the world’s natural pearls.¹¹ Cultured pearls became commercially important in the 1920s, at about the time natural pearl production began to decline.³ The page who invented cultured pearls tells how that happened. Natural pearls can still set records: in 2018, Marie Antoinette’s 18th-century natural pearl and diamond pendant sold for CHF 36,427,000.⁶ The page famous pearls has more such stories.

How labs tell natural and cultured pearls apart#

Natural and cultured pearls can look the same, so labs look inside them. The first gem testing laboratories, starting with London’s in 1925, first focused on telling them apart, and X-ray radiography remains an essential method for the job.⁹ A natural pearl shows no bead or curved cavity at its center, and a uniform, onion-like structure.²

Natural pearl

• Formed with no human help
• Even, onion-like layers to the center

Cultured with a bead

• A person implants a shell bead
• The bead shows under the nacre

Cultured without a bead

• Started with tissue alone
• An organic-rich center or a void
• The hard cases for labs

Text version of this diagram

Three pearls cut in half. The natural pearl has even, onion-like layers all the way to its center, and no bead. The pearl cultured with a bead has a large shell bead in the middle, with layers of nacre around it. The pearl cultured without a bead has layers of nacre around an organic-rich center or a small void, and its inside can look much like a natural pearl’s.

Pearls grown without a bead are the hard cases. Non-bead cultured pearls, often sold as keshi, can have internal features much like those of natural pearls.¹² In 2010, SSEF warned that beadless cultured pearls, some sold with reports calling them natural, were entering the natural pearl trade.¹³

How natural and cultured pearls are named#

In the United States, the unqualified word “pearl” may only be used for a natural pearl, one whose formation was in no way caused or induced by humans. A cultured pearl must be called “cultured” or “cultivated”, in letters as clear as the word “pearl”.¹ CIBJO’s standards say the same, and recommend labeling natural pearls as “natural pearls”.⁸

Labs record the difference in weight too. GIA and SSEF weigh loose natural pearls in carats and in grains, where 1 grain is 0.25 carat, and loose cultured pearls in carats only.^{4 5}

Choosing between natural and cultured pearls#

Choose natural pearls if you want a rarity with a long history, and buy them only with a recent report from a gem laboratory that states they are natural.⁵

Choose cultured pearls if you want a wide choice of types, sizes and colors. The pearl types section describes each one.