June’s birthstone, the pearl, pure and fair to the eye, has been recognized since the earliest times as the emblem of modesty, chastity, and purity. A fine natural or Oriental pearl-the real “genuine pearl” – is considered a precious gem since they are relatively rare in nice sizes today. The pearl business is almost entirely in the cultured pearl market.

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Assessing Pearl Quality

Pearls are produced by oysters (not the edible variety) in salt water and by mussels in freshwater lakes and rivers. They produce the pearl nacre naturally, and it takes years to produce a fine, large pearl. As with all things, quality and value vary. The quality and value of the genuine natural pearl are determined by:

• Free from surface blemishes (blisters, pimples, or spots).

• Roundness : the more perfectly round, the better.

• Luster : the higher the luster, the better (luster may be called Orient by some gemologists).

• Tint : rose-tinted pearls are considered the most valuable, although there are also white and cream-colored pearls that are highly desirable.

• Size : Oriental pearls (natural) are sold by weight.

Pearls are weighed as “grains” (conventionally, 4 grains equals 1 carat). Cultured pearls are measured in millimeters. The larger the pearl, the greater the cost, jumping dramatically, for example, between 7.5mm and 8mm, which is considered large; or between 9 and 10 mm, which is very large both in size and in price. The price jumps upward rapidly with each millimeter once you pass 8 mm.


A fine pearl necklace, or any strung pearl item, requires very careful matching of size, roundness, luster, tint, and skin texture. Graduated pearls-a strand containing larger pearls in the center, with the pearls becoming progressively smaller toward the ends – also require careful sizing. Failure to match carefully will detract from both the appearance of the piece and its value.

Pearls should be handled with care. It is best to keep them in a separate pouch and to exercise some caution when wearing them to avoid contact with certain substances such as vinegar (when making a salad), ammonia, inks, and certain perfumes since these can spot the pearl’s surface.

Also, the frequent application of hair spray while wearing pearls will coat them and make them very dull, but this coating can be cleaned by washing in nail polish remover.

The Pearl Market Today Is a Cultured Pearl Market

When we speak of pearls today, we are usually referring to cultured or cultivated pearls. The cost of fine cultured pearls has become very high and continues to rise. Cultured pearls are usually produced by inserting a mother-of-pearl bead into the mantle (tissue) of a live oyster and then returning it to the water.

Over time (usually several years), the oyster secretes a coating of nacre over it, a coating rarely thicker than 0.5 mm. The thickness depends in part upon the length of time the bead remains in the oyster.

Sometimes the cultured pearl is removed from the oyster prematurely so that the nacre coating is too thin and may begin to wear through in only a few years. In other cases, the cultured pearl is so fine as to require an expert to tell it from a fine, genuine natural pearl.

In terms of quality and value, the same factors are used to determine the quality and value of a cultured pearl as for a natural pearl.

But a pearl must always be clearly described as cultured or genuine (oriental), and this should be stated in writing on your bill of sale since Oriental pearls are much more costly than cultured pearls.

Biwa And Other Freshwater Pearls

Biwa pearls are grown in freshwater (lakes and rivers) and derive their name from Lake Biwa in Japan, where very fine freshwater pearls are grown. Until recently, the term “Biwa” was often used for any freshwater pearl.

Today it is used only for those from Lake Biwa. Freshwater pearls are grown in many countries, including the United States, China, and Ireland, using common mussel-type mollusks are used.

The process does not require the insertion of a mother-of-pearl bead, so the pearls grow much faster, and each mussel can simultaneously produce many pearls (unlike the saltwater oyster, which normally produces only a single pearl).

As a result, most freshwater pearls are much less expensive than saltwater pearls. The most familiar freshwater pearls have long, narrow, rice-shaped outlines. They can also be round, but these are rare and expensive. They can be smooth or wrinkled and come in many lovely colors.

What are Baroque Pearls?

Baroque pearls are both genuine (natural) and cultured. Their shape is more or less irregular, but they are distinctive because of their very beautiful tints of color.

Their irregular shape renders them far less valuable than round pearls. Nonetheless, they make beautiful, versatile fashion accessories (earrings, bracelets, pendant pieces).

Is the Color Natural?

Cultured pearls are available in many colors-gray, black, pink, and blue-but often, these colors have been produced by surface dyes.

White pearls that have been tinted and then drilled for jewelry use (as in a necklace) can be easily detected by a qualified gemologist.

Is It Real or Simulated?

Simulated or imitation pearls are sold everywhere. Many of the finest imitations have been mistaken for fine cultured pearls. One test is to run the pearl gently between your teeth (the tooth test).

The cultured or genuine pearl will have a mildly abrasive or gritty feel, while the imitation will be slippery and smooth.

(This test won’t work with false teeth.) Try the test on pearls you know are cultured or genuine, and then try it on known imitations to get a feel for the difference. But once again, when in doubt, seek out a qualified gemologist. The cost may be too great to risk it.

Price Ranges for Various Pearls

PearlTypical Color(s)Cost per sizeAvailability
Round (cultured)Silver, silver
pink white,
Matched pairs :7.5 mm: $40-$250
8.5 mm:
9.5 mm:
16" strand-uniform:
$900- $4,500
8.5 mm:
$3,000- $36,000
high quality pearls over 8mm are rare
South Sea (cultured)Silver, silver
pink white,
white, cream
16" strand-
10-14.5 mm:
$15- $150,000
11-16 mm:
rare to find fine quality pearls over 16mm
Baroque (cultured)White to creamy white16" strand-uniform.
7-8 mm:
8-9 mm:
Good quality pearls are readily available in this size range.
Freshwater (cultured)Available in all colors16" strand:
Rice shaped
4-5 mm: $40-$180
6-7 mm: $140-$450
4-5 mm: $120-$225
6-7 mm: $140-S450
Round (cultured)Black/Gray (dyed)16" strand-uniform:
5-6mm : $900, 7-8mm: $2,200, 8-9mm: $3,500
Good (natural
gray color are rare;
much more
than dyed)

Fully drilled pearls mounted on a gold “post” sell for much less than undrilled pearls.

A Final Word

There are innumerable differences in quality – if roundness is good, luster may be poor; if luster is good, roundness may be poor; if color and luster are good, there may be poor surface texture from too many skin blemishes or matching in a strand may be poor.

Shopping around can teach you a tremendous amount about pearls. Do not visit just a single online or brick-and-mortar store prior to making a purchase decision. Keeping in mind the factors that affect quality size, luster, color, roundness, and skin blemishes – go window-shopping and compare.

You may find you like a certain color or luster but can’t afford a strand of 8-mm pearls, but would be just as happy with 7 mm, which are considerably cheaper.


Mamangkey NG, Agatonovic S, Southgate PC. Assessing pearl quality using reflectance UV-Vis spectroscopy: does the same donor produce consistent pearl quality? Mar Drugs. 2010 Sep 20;8(9):2517-25.

Tani Y, Nagai T, Koida K, Kitazaki M, Nakauchi S. Experts and novices use the same factors–but differently–to evaluate pearl quality. PLoS One. 2014 Jan 22;9(1)