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GIA GEMOLOGICAL INSTITUT!:: OF AMERJCA

Table of Contents

Subject Page

The Pearl-Bearing Mollusk . . . . . . . . . . . . . . . . . . . . .・・ a・・ ・・・ ・・..・・・・・・ ・・.. 1 Natural Pearls ................................................. 3 Structure of a Saltwater Cultured Pearl .............................. 3 Structure of a Freshwater Cultured Pearl ..............・・・ ・・・・・・・・ ...3

Today's Cultured Pearls .............................................3

Grading Environment ............................................... 6

The Seven Value Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Grading Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Value Factor 1: Size . . . . . . . . . . . . . . . . . . . ・・ ・・・・・・・・・・・ ・・・・・・ ......7How to Measure Pearls . . . . . . . . . . . . . . . . . . . ， • • . • . • • • • . • . • . • . • . • 8

Valu巴Factor2: Shape ........................................... 8 Shape Classifications ........................................ 8 How to Observe Shape . . . . . . . . . . . . . . . . . . . .白・・・・・・・・ ・.........9

Value Factor 3: Color . . . . . . . . . . . . . . . . . . . . . . . . . . . . .・・・・・・白 ........9Hue Circl巴 ....................，.....，.. .・ ・...................lO

Pearl Color Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Neutrals ................................................. 1 Near-Neutrals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Hu巴Terms............................................... 13 Tone and Saturation Terms .................................. . 1 J GIA Pearl Color Terminology Grids ..... . . . . . . . . . . . • . . . . . . . . 14， 15 Overtone Terms .........................................‘ .16

Noting Orient . . . . . . . . ・・・・・・・ ・・・ ・・・・・・・ ・・・・・・ .............]6 How to Observe Color ...................................... 16

Bodycolor. . . . . . . . . . . . . . . . . . . . . . . .・・・・・・・・・・・・ ・・・・ .•• ....16

Overtone. .・・・・・・・・・・・ ・・・・・・・・・・ ー・・・・・・ ・・・ ・・・・・・ ・・・ ..... 17 Orient ..........................・・・・・・・・・ ・・ ・・・・ ・ .. . 17

Value Factor 4: Lust巴r.......................................... 17 Luster Classifications ....................................... 17 How to Observe Luster . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Value Factor 5: Surfac巴Quality.， • • • • • • • • • . • • • • . • • • • • . • . • • • • • • . • . • 18 Types of Blemishes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Surface Quality Classifications . . . . . . . . . . . . . . . . . . . . . . . .白.. . . . . . 18 How to Observe Surface Charact巴ristics.... . . . . . . . . . . . . . . . . . . . . . 19

Valu巴Factor6: Nacre Quality .................................... 20 Nacrl巴 QualityClassifications ................................. 2() How to Observe Nacre Quality . . . . . . . . . . . . . . . . . .・・ ・...........20

Value Factor 7: Matching . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . .20 Matching Classifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ; . . . . . . 21 How to Observe Matching ................................... 21

Post-Harvest Processing and Treatments ........ . . . . . . . . . . . . . . . . . . . . . . . . 21 Common Post-Harvest Processing ......... . . . . . . . . . . . . . . . . . . . . . . . .21 Treatments and Detection . . . . . . . . . . . . . . . .白....'.............0..一...21

Pearl Identification: Natural， Cultured， lmitation . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Identifying Natural and Cultured P巴arls. . . . . . . . . . . . . . . . . . . . . . . . . . . . .22 Identifying lmitation Pearls ...................................... 23

Care and Cl巴aning. . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . • . . . . .・・・・・・ ・.23

Value Factor Chart ........................・・・・・・・・・・・・・・・ ・・・ ..24，25

Pearl Industry Associations . . . . . . . . . . . . . . . . . . . . . . .ー ・・・・・ ・・・・・・...・..26

Pearl Grading Worksheet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .・..• • • • 27

Q~~r~~ l~vQ~~g，~，p.g The GIA Pearl Description System applies to natural and cultured saltwater and j陀shwaterpearls.

THE PEARL圃 BEARINGMOLLUSK Pearls， whether natural or cultured， are formed inside mollusks. There are many species of mollusks that can produce pearls. But only a few of these species， whether in salt water or fresh water， are responsible for the over-whelming m句orityof today's pearls.

These include three saltwater pearl mollusks:

Pinctaぬかcata，commonly called the akoya oyster. 11's found in the coastal waters of Japan， China， Australia， and New Guinea， and is the species originally used in Japan for the first commercial cultured pearls.

Pinctada margaritifera， or black-lipped oyster. This species is found throughout the southern Pacific， particularly in French Polynesia. 1t pro-duces Tahitian pearls， which are primarily black or gray.

Pinctad，αmaximα， or silver-lipped and gold-lipped oysters. Found throughout much of the southern Pacific， this species produces the large white or golden color South Sea pearls.

Freshwater mollusks， also called mussels， include:

Cristaria plicata， commonly called wrinkle shell or river shell. This mussellives in the rivers and lakes of China， Vietnam， Japan， and Korea，

and was the origin of the large volume of Chinese freshwater pearls pro-duced during the 1970s and 1980s.

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The Pinctada margaritifera oyster pro-duces the Tahitian pearl.

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Hyriopsis cumingi， or triangle shell. This mussel is found in China.

Cristaria plicaωand Hyriopsis cumingi mussels account for the majority

of Chinese freshwater pearl production today.

Megalonaias nervosa， or washboard. Although several species from the

Unionidae family have been used to culture pearls in North America， today virtually all are produced in M. nervosa.

All pearl-producing mollusks have one thing in common: They build a

mother-of-pearl lining inside their shells. Only mollusks that can do this

can produce a nacreous pear1. The substances that make up the pearl and the shell lining are the same materials. The iridescent lining on the inside

of the shell is called mother-of-pearl; when it's on the pearl， it's called

nacre.

The mantle is an organ within a pearl-producing mollusk that manufac-tures both conchiolin and calcium carbonate-the essential building blocks

of both the mollusk's shell and pearls.

Conchiolin is an organic compound similar to material found in human hair and fingernails.

Calcium carbonate is a compound of calcium， carbon， and oxygen

(CaC03). It crystallizes in two di百.erentforms called aragonite and calcite.

A mollusk shell has three layers. The rough， outer layer， called the

periostracum， is composed entirely of conchiolin. The middle section，

called the prismatic layer， is mostly calcite. And the smooth， shiny mother-of-pearllining is primarily aragonite. (See illustration below.)

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This is an expanded view of a mollusk shell showing the mother-of-pearl layer (A)， the prismatic layer (8)， and the periostracum (C). Adapted from Saquet & Dilhan (199刀

NATURAL PEARLS A natural pearl forms when a parasite or some other foreign matter enters the body of a pearl-producing mollusk. The mollusk deposits layers of nacre over出eintruder to soothe the irritation.

Structure of a Saltwater Cultured Pearl Saltwater cultured pearls form when a bead nucleus and a piece of mantle

tissue are inserted into the mollusk. This process is called bead nucleation. The mollusk first deposits a layer of conchiolin over the bead nucleus. It then deposits nacre， which is composed of platelets of aragonite. A small amount of calcite might be mixed in with the aragonite. Researchers sus-

pect that pearls with poor luster probably have more calcite in their nacre than pearls with better luster.

Structure of a Freshwater Cultured Pearl For freshwater cultured pearls， the typical culturing process starts when a piece of mantle tissue is inserted into the mussel. This is called tissue nucle-ation. Although a bead isn't inserted， the host mollusk reacts to the intrud-

ing tissue in the same manner as with bead nucleation. First it secretes a

layer of conchiolin， then layers of nacre. Tissue-nucleated pearls are almost entirely nacre.

Some freshwater culturing operations employ bead nucleation. The result is a pearl similar in appearance to saltwater cultured products.

TODAY'S CULTURED PEARLS Today's cultured pearl jewelry market includes a wide range of products.

Akoya-These saltwater pearls紅 ecultivated primarily in Japan and China.

The typical size range is from 6 mm to 7 mm， but you might see them as small as 2 mm or as large as 10 mm. Most akoya pearls have a white to cream bodycolor. Other natural colors， including yellow， gray， and blue，紅e

possible.

South Sea-Australia， Indonesia， and the Philippines are the principal areas for commercial farming of these saltwater pearls. They range in color

from white to golden， and occur in other colors， too. They typically range in size from 8 mm to 15 mm.

Tahitian-Cultivated primarily around the islands of French Polynesia， these saltwater pearls range in color from white to black to other colors， including green and pu中le.The typical size range is 8 mm to 14 mm， although larger pearls are produced in limited quantities.

Freshwater-Freshwater pearls are found in a large range of sizes， shapes， and colors. China is the primary source for today's freshwater pearls. Japan and the United States produce small crops.

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A strand of 6.0・6.5mm akoya cultured pearls.

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A necklace of baroque-shaped South Sea cultured pearls.

Chin巴sefreshwater cultured pearl strands of various dyed colors

A strand of white freshwater cultured pearls

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Robert Won Collection

Tahitian cultured pearl necklace with rose and gre巴nove吋ones.

Latendresse Fomily. Nashville. Tennessee

A Dome pearl， a brand name of an American pearl producer， is a blister pearl that retains pa吋 ofthe surrounding host shell

A colorful mix of keshi pearls.

Mabe pearls are assembled by filling hollowed blister pearls with resin and apply-ing mother-of-pearl backings.

Keshi-Keshi (Japanese for“poppyseed") pearls are accidental byprod-ucts of saltwater and freshwater culturing processes. Generally irregu-

larly shaped， keshi come in a variety of sizes and colors. Most likely，

they occur in one of two ways. In the first， the mollusk expels the

implanted nucleus， but the mantle tissue implant remains， stimulating

keshi pearl production. In the second instance， the mollusk is successful

in depositing nacre around the nucleus to form a cultured pearl. In addi-

tion， dislodged cells from the mantle tissue trigger the growth of keshi pearls.

Blister-Blister pearls grow attached to the mollusk's shell. One side is

flat and without nacre. They're cultured in saltwater and freshwater mol-

lusks.

Mabe-Mabe pearls are assembled cultured blister pearls. They're cut

from the shell， and the nucleus is removed. The resulting void is filled

with epoxy resin (and sometimes a bead) and glued to a mother-of-pearl

backing.

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Daylight-equivalent light source.

This is a recommended environment for consistent pearl grading.

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GRADING ENVIRONMENT Lighting， background colors， and other environmental factors impact your ability to consistently examine and describe pearls.

Background-Use a neutral gray pearl board. Remove brightly colored objects from the area. Wear neutral colors.

Light Source-A daylight-equivalent f1uorescent light source is most commonly used. The light source should illuminate the work area and be placed approximately 20 to 25 cm (8 to 10 in.) above the pearls.

Position-You should be approximately 30 cm (12 in.) from the pearls. Lay the pearls on the pearl board. Roll or rotate the pearls to get an overall

lmpressIOn.

Comparison Pearls-Reference pearls or strands with known characteris-tics often help achieve greater grading consistency.

Magnification-None required.

THE SEVEN VALUE FACTORS These seven factors a百ectpearl value:

1. Size

2. Shape

3. Color

4. Luster

5. Surface Quality

6. Nacre Quality

7. Matching

Size-Size is measured in millimeters. For spherical pearls， measure the diameter; for other shapes， measure the length and width.

Shape-There are three main categories of shape: spherical， symmetrical， and baroque. There are seven standard shapes that fall into these categories.

Color-Pearl color has three components: bodycolor， overtone， and orient. Bodycolor is the overall color of the pearl. Overtone refers to one or more noticeable translucent colors that overlie the bodycolor. Orient is a form of iridescence that appears to be on or just below the surface. Not all pearls display all three characteristics.

Luster-Luster is the light ref1ected from the surface of the pearl. It's described by its intensity.

Surface Ouality-Most pearls have surface characteristics， or irregulari-ties. Surface condition is judged by the size， number， location， visibility， and types of blemishes. Blemishes a旺ectthe pearl's appearance; some a百ectboth appe紅 anceand durability. Few pearls are completely blemish-free.

Nacre Quality-Nacre quality is deterrnined by its thickness and layering. If the nucleus is visible， the nacre is too thin. A chalky appearance might result from thin nacre or poor nacre layering.

Matchingー Matchingdescribes the uniformity of pearls in jewelry. It depends on the consistency of the other six factors. It takes time and inventory to sort and collect pearls for a single strand. That's true even if the pearls are intentionally mismatched. Matching is not a true pearl qual-ity factor， but it does impact value. Matching does not apply to single pearls.

GRADING PROCEDURES

Value Factor 1: Size Pearl measurements are stated in millimeters and rounded to the nearest 0.5 mm. For individual spherical pearls， measure the diameter and state the size as one measurement-6 mm， for example. For individual pearls of any other shape， measure the length and width of the pearl; 12 mm x 15 mm， for example.

When stating the size of pearls in a strand， give the diameter mea-surement. The diameter is the measurement taken perpendicular to the drill-hole. State the size as a range of half (Y2) a millimeter; 6-6Y2 mm or 6・6.5mm， for example. The larger pearls訂 ein the center， and the small-er pearls are at the ends.

A graduated strand labeled 3-7 mm contains pearls that range in size from 3 mm to 7 mm in diameter. You might also see this expressed as 7-3 mm.

Pearls can range from 2 mm to more than 20 mm in size. The largest pearl shown is approximately 18 mm.

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For strands of pearls， state the diame-ter measurement perpendicular to the drill-hole as a range.

How To Measure Pearls Pearls are relatively soft. Handle them with care when you measure them so you don't scratch or mar the surface. Use a Leveridge gauge or one of

the special pearl gauges to measure them.

Value Factor 2: Shape There are seven standard shapes.

Shape Classifications

SPHERICAL

Round-appears round to the eye.

Near-round-appears almost round to the eye. Some might be slightly out-

of-round， elongated， or f1attened.

SYMMETRICAL

Oval-symmetrical， rounded， oblong shape.

Bu悦on-symme住ical，f1attened or slightly f1attened， c廿cul紅 shape.Can be a high button or low button.

Drop-symmetrical， rounded， pear shape. Can be a long drop or short drop.

BAROQUE

Semi-baroque-non-symmetrical， off-round， slightly irregular oval，

button， or drop shape.

Baroque-non-symmetrical shape-will have a noticeably irregular appearance.

For any shape other than the seven standard shapes， describe the shape as it appears-bar， cross， or coin， for example.

Some pearls have one or more grooved or ridged rings around the cir-cumference. If the grooves extend around the entire circumference of the pearl， describe it as a circled pearl. Use the shape category along with the circled modifier-for example， circled drop.

Semi-baroque South Sea cul-tured pearl.

A strand of near-round akoya cultured pearls.

A strand of baroque akoya cultured pearls.

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This strand is made up of circled Tahitian cultured pearls. Some show green and rose overtones.

How to Observe Shape

Describe cultured freshwater pearls in fancy shapes like bars (Ieft) and cross-es (right) as they appear.

Button (far left p巴arlin strand above)，

oval (Ieft， above)， and drop (right， above) pearls are symmetrical shapes.

Roll the pearl(s) on the pearl board， then pick the pearl(s) up and rotate

them between your fingers above the board. Note your overall impression of the shape based on the classification descriptions.

• Mark the appropriate shape on the worksheet.

• If the pearl is circled， also indicate that on the worksheet.

Value Factor 3: Color Pearls come in a variety of natural colors. The most common are actually

neutral or near-neutral colors: white， gray， black (neutral) and silver， cream，

brown (near-neutral). Freshwater， South Sea， and Tahitian pearls expand

this palette to include many other colors.

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Hue Circle

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Pearl color can have three characteristics:

• Bodycolor-The dominant， overall color of the pearl.

• Overtone-One or more translucent colors that appear over the body-color.

・Orient-Iridescent，rainbow colors shimmering on or just below a pearl's surface. Pearls with irregular surfaces are more likely to exhibit orient.

Color has three attributes: hue， tone， and saturation. Hue is the basic impression of color-yellow， green， blue， for example. Tone is the relative impression of lightness or darkness of the color. Saturation is the strength or intensity of the color.

Color description systems can v紅yfrom the simple to the complex. In

describing pearl color， it's important to use descriptions that have enough

Warm

Cool

The GIA Pearl Description System recognizes these 19 hues to describe fancy-colored pearls.

Warm

Tahitian cultured pearls with yellowish green bodycolor. The center pearl displays rose overtone.

A strand of white akoya cultured pearls

Tahitian cultured pearls might or might not display overtone. The dark brown pearl at right shows rose overtone

Latendresse Family. Nashville. Tennessee

A range of color appearances from white to pink is common in freshwater cultured pearls.

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South Sea cultured pearls with yellow and cream bodycolor and no overtone.

(Left) Oark gray Tahitian cultured pearl with rose overtone and (right) Tahitian cultured pearl with bluish gray bodycolor.

Latendresse Family. Nashville. Tennessee

Fancy-colored cultured pearls come in a rainbow of hues.

South Sea cultured pearl with silver bodycolor.

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Latendresse Family， Nashville， Tennessee

White to orange bodycolor is common in freshwater cultured pearls.

These Tahitian cultured pearls， with green gray bodycolor， and rose， blue， and purple overtones， are often referred to in the trade as "peacock."

Latendresse Family， Npshvllle， Tennessee

The shimmer of rainbow colors seen on these freshwater cultured pearls is called orient

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Yellow South Sea cultured pearl (this type of color is sometimes referred to as、olden"in the pearl trade).

Green and blue dominate the bodycol-or of these Tahitian cultured pearls.

A strand of cream-colored akoya cultured pearls.

detail to describe the color， are understandable to a broad audience， and are

repeatable from observer to observer. While the human eye can distinguish

a very large number of colors， describing each of these individual color sen-sations is not practical nor repeatable. That's why the GIA Pearl

Description System groups color appearances into discrete ranges. These

ranges， in tum， can be defined and described with color terminology.

Pearl Color Terminology The GIA system for describing pearl color uses 19 hue names， the neutrals

(white， gray， and black)， and the near-neutrals (cream， silver， and brown).

If the tone of the pearl is light or dark， state it. Use the terms “gray/gray-

ish" or “brownlbrownish" to describe the appearance of various hues as the

saturation decreases.

Some of the hue names used in the GIA system match industry terms

that are widely recognized and defined. This includes the term“pink" for

lighter versions of red in hues like reddish orange， orangy red， red， pu1'-

plish red， and reddish purple. Some other examples a1'e the use of “cream"

fo1' light yellow to orange colors and “silver" fo1' light cool colors like

blue.

When assessing pearl colo1'， replace the terms“hue" and “hueish" with

the actual color you're describing.

Neutrals

• White

• Gray

・Black

Near-neutrals

• Silver

• Cream

• Brown

Hue Terms

• Red (Pink)

• Orangy Red (Orangy Pink)

• Reddish Orange (Pinkish Orange)

• Orange

• Yellowish Orange

• Orangy Yellow

• Yellow

• Greenish Yellow

• Yellowish Green

• Green

• Bluish Green

• Blue Green

• Green Blue

• Greenish Blue

• Blue

• Violet

• Purple

• Reddish Purple (Pinkish Purple)

• PU叩lishRed (Purplish Pink)

Tone and Saturation Terms

The terminology grids on Pages 14-15 and on Pages 2・3in the Color Reference Charts illustrate the general relationship of color terms for warm and cool colors in the GIA Pearl Description System. Typically，

as saturation decreases， warm colors， like yellow or orange， appear more brown. But cool colors， like blue or green， appear gray. Tone is described along the vertical axis. Tone ranges from light at the top to dark at the bottom. Saturation is described horizontally on the grid. It increases in intensity from weak at left to strong at right.

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GIA Pear1 Color Terminology Grid Warm Hues

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gray hueish hue hue strong

brown bro馴 hue

dark hueish hue hue gray brown brown

black dark dark dark dark brown hueish hue brownish

brown brown hue

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PEARI DESCIt'I'III1N SYSTEM MANUAL

GIA Pearf Color Tenninology Grid Cool Hues

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light light light light gray hueish hue hue

gray gray

gray hueish hue hue S岡崎

gray gray hue

dark hueish hue hue gray gray gray

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As you can see on the grid， the left vertical column consists of the neu-trals-white， gray， and black. The descriptions in this column describe pearls that are white， light gray， gray， dark gray， and black. As you move away from neutral gray to the first saturation level (hueish brown/hueish gray)， the color appearance is still quite close to the neutrals and is described as predomi-nantly gray or brown. For example， greerush gray or pi叫dshbrown. At the next level， the strength of the hue and the gray or brown is approximately the

same (hue brown/hue gray). When the hue becomes strong enough， the gray/brown term is ornitted from the color name (hue). Notice that the color descriptions for w紅 mhues and cool hues vary at the dark -tone level.

Overtone Terms

In addition to bodycolor， a pearl might have one or more translucent over-tones. Some of the most common are:

• Rose

・Green

• Blue

Other colors are possible. Note any color you see.

Noting Orient

In addition to bodycolor and overtone， you might see orient. Simply check Yes， if present， or No if not.

How to Observe Color Follow these steps to color grade pearls:

• Use consist芯nt，controlled lighting and viewing environment (see Grading Environmenl， Page 6).

• Rol L the pearl(s) on the pearJ board， then pick the pearl(s) up and rotate them between your fingers above the board.

• When possible， use master color comparison pearls for consistent color evaluation. An altemative is to use your Color Reference Charts. Arrange

the master pearls parallel and close to， but oot touching， the pearls yOll 're grading.

• Ddermine bodycoJor flISt， then overtone， and .finaUy orient. If you detect color rrealmellt at any point， noLe il 0]) your worksbeet.

Bodycolor

Tbe bodycolor is the dominant， overall color appearance of the pearl. If there is an overtone， the bodycolor is best observeu at the outer rim of山epearl.

• Select the appropriate bodycolor from the color classifications.

• Compare lhe body<..:olor of the pearl to be described to your color refer-巴nces.If applicable事 compω.ethe color to the lighter side and the darker side to deterτnine lbe tone range.

• Compare the bodycolor to your color references. Compare the color to the weak:er side and the stronger side to determine the saturation range.

• Locate this range on your color terminology grid and write the co汀e-sponding bodycolor description on the worksheet.

Overtone

Some pearls might have no overtones， others might have one overtone， and still others might have multiple overtones.

• Locate the reflection near the top of the pearl. Overtone is the presence of color seen in that reflection.

• When examining a strand， determine the overtone classification based on

the majority of pearls.

• Write the overtone description on the worksheet.

Orient

Pearls with irregular surfaces， for example， baroque shapes， are more like-ly to display this color component.

• Roll the pearl(s) on the pearl board， then pick the pearl(s) up and rotate them between your fingers above the board.

• Look for the presence of two or more rainbow-like colors (pink， green， yellow， orange， blue) on or just below the surface as you rotate the pearl.

• When examining a strand， include orient in the color description only if the majority of the pearls display it.

• Mark it on the worksheet.

Value Factor 4: Luster Luster is the intensity of light reflected from the surface of the pearl. There are four categories of luster.

Luster Classifications Excellent-Reflections are bright， sha中， and distinct.

Good-Reflections are bright but not sharp. They're slightly hazy around

the edges.

Fair-Reflections are weak， hazy， and blurred.

Poor-Reflections are dim and di百used.

How to Observe Luster • Roll the pearl(s) on the pearl board， then pick the pear1(s) up and rotate

them between your fingers above the board.

• Look for reflections of the grading light on the surface of the pearls.

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The luster of these akoya cultured pearls ranges from excellent (top) to fair (bottomト

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An abrasion is a series of scratches on the surface. This pearl shows parallel abrasions around its diameter.

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Irregular bulges， blisters， or welts are called bumps.

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Cultured pearls showing excellent luster (Ieft)， good luster (center)， and poor luster (rightトLusteris judged on the brightness and sharpness of the light a pearl reflects.

• Judge the luster by the brightness and sharpness of the reflected light. When evaluating a strand， note the overall impression of luster from the majority of pearls.

• Mark the luster classification on the worksheet.

Value Factor 5: Surface Quality Surface quality is the condition of the pearl's surface. Blemishes or irregu-

larities are characteristic to pearls and紅 'eusually confined to the I)urface.

Types of 81emishes Abrasion-A series of scratches on the surface of the pearl.

Bump-An irregular bulge， blister， or welt; usually too small to a町ectbasic shape.

Chip-An opening or cavity in the surface.

Crack-A surface-reaching break or frac佃rein the nacre， or a break or

fracture in the nucleus.

Flat-A flat section on an otherwise spherical pearl; usually too small to a旺ectbasic shape.

Gap-An area where the nacre has not covered the nucleus.

Pit-An indentation or depression; found individually or in a group.

Scratch-A thin groove or depression in血esurface.

Spot-An area that is darker， lighter， or more dull than the surrounding nacre.

Wrinkle--An irregul紅 ridgeor crease on the surface.

Surface Quality Classifications Clean-Pearls can be blemishサ'eeor contain minute surface characteris-

tics血atare difficult for a trained observer to see. If the pe紅 Is紅 ecom-pletely blemish-free， add the notation Spotless to the comments section of the worksheet.

Lightly Blemished-Pearls show minor surface irregularities when inspected by a trained observer.

〆¥

A cavity in the pearl surface is called a chip.

/

¥

A break in the pearl surface is called a crack

PfARL IIFSr:ntPTION SYSTlM MI¥NIlAI

〆

Dents called pits are another type of blemish.

¥

A spherical pearl's surface is some-times blemished by a flat section.

Areas where nacre has not covered the Scratches are thin grooves in the pearl nucleus are called gaps. surface.

/

Patches called spots are darker， lighter， or duller than the surrounding nacre.

Moderately Blemished-Pearls show noticeable surface characteristics; a

few might be quite noticeable.

Heavily Blemished-Pearls show obvious surface irregularities. Durability

rnight be a百ected.

How to Observe Surface Characteristics • Roll the pearl(s) on the pearl board， then pick the pearl(s) up and rotate

them between your fingers above the board.

• Consider the size， number， location， visibility， and types of surface char-

actenstlcs present.

¥ /

Wrinkles are irregular ridges or creases on the pearl's surface.

19

GIA PEARL liliAUI山日

Cultured pearls on this akoya strand look chalky， indicating thin or poor quality nacre

20

Tahitian cultured pearl with clean surface. Tahitian cultured pearl， lightly blemished

Tahitian cultured pearl， moderately Tahitian cultured pearl， heavily blem-blemished. ished.

• Mark the appropriate surface quality classification on the worksheet.

• Base your evaluation on the surface characteristics of the majority of

pearls.

Value Factor 6: Nacre Quality Nacre quality is determined by its thickness and layering. Nacre quality can

be classified in three ways.

Nacre Quality Classifications Acceptable-Nucleus not noticeable; no chalky appearance.

Nucleus Visible-Pearl(s) show evidence of bead nucleus through the

nacre; pearl(s) show blinking when rotated.

Chalky Appearance-Pearls have an obvious dull appearance.

How to Observe Nacre Quality • Roll the pearl(s) on the pearl board， then pick the pearl(s) up and rotate

them between your fingers above the board.

• Mark the appropriate nacre quality classification on the worksheet.

Value Factor 7: Matching Matching describes the uniformity of pearls in jewelry. Judge the consis-

tency of size， shape， color， luster， surface quality， and nacre quality among

the pearls.

For pearls that are intentionally mismatched， look for overall harmo-

nious design and balanced effect. Matching can be classified in three ways.

Matching Classifications Excellent-Pearls are uniform in appearance and drilled on-center.

Good-Minor variations in uniformity; classification is based on the severity of variations.

Fair-Noticeable variations in unifoロnity;classification is based on the

severity of variations.

How to Observe Matching • Roll the pearls on the pearl board， then pick the pearls up and rotate them

between your fingers above the board.

• Judge the consistency of each value factor: size， shape， color， luster， sur-face quality， and nacre quality.

• Note your overall impression.

• Mark the appropriate matching classification on the worksheet. Comment on intentionally mismatched pearls. Mark N/A for a single pe紅 l

POST-HARVEST PROCESSING AND

TREATMENTS Most cultured pearls undergo some type of post-harvest processing. These procedures generally include cleaning and buffing the pearls， and don't dra-

matically alter their appearance.

Off-color pearls might be dyed or irradiated to peロnanentlychange their color. These are considered treatments.

Common Post-Harvest Processing These processes are usually undetectable.

Cleaning-Cleaning removes residue the mollusk left on the pearl.

Bleaching-Bleaching removes dark areas. Tahitian and South Sea pearls

are seldom bleached.

Buffing-Buffing， with or without a polishing compound， removes surface

imperfections.

Treatments and Detection Dyeing， irradiating， and coating are considered treatments.

Dyeing一一Dyeingalters the basic pearl color.

Detection:・Dyedpearls might appear mottled in color. When examined under magnification and with a strong light source， color concentrations

1・IA'II IIfs，:n，pnlllll SYSTr仇11MANIIA'

Akoya strand with fair matching-pearl colors vary.

Akoya strand displaying excellent matching-pearls are uniform in size， shape， color， luster， surface quality， and nacre quality.

21

l主

This strand shows akoya cultured pearls dyed to an intense yellowish orang巴.

Treated blue akoya strand shows evidence of dyeing.

..・B・E・晶 |

!faFT¥旬、~寄.・. .'

合|

Natural pearls， like those in this X-ray， have no nucleus.

22

from the dye might appear in surface depressions or in streaks just below

the surface. If the pearls are dri1led， color concentrations are often found around the dri1l-hole.

Irradiation-Irradiation permanently alters the pearl's color.

Detection:・Ifthey're irradiated， freshwater pearls often exhibit very

intense， metallic-like colors. In some natural-color saltwater pearls， you

might also see metaI1ic-like colors. In bead-nucleated pearls， if a drill-hole is present， you might see a dark bead nucleus.

Coating-Coatings enhance the luster of pearls and are usually used on

lower quality goods. The e町'ectmight not be permanent.

Detection: Careful examination under magnification might reveal evi-dence such as coating material unevenly deposited in surface depressions.

In addition， the surface might feel too smooth to the touch or when put to

the tooth test (see Page 23).

If in doubt， submit pearls to the GIA Gem Trade Laboratory for identifi-

catlOn.

PEARL IDENTIFICATION: NATURAL， CULTURED， IMITATION

Identifying Natural and Cultured Pearls Conclusive identification of natural origin is possible only with two

sophisticated laboratory test procedures: Xィadiographyand X-ray fluo-rescence.

The bead nucleus is more dense and thus less transparent to X-rays than

the surrounding nacre and conchiolin. Therefore， a demarcation line around the bead nucleus wiI1 be visible on the photographic film.

X -ray luminescence provides indications of the fresh-01' saltwater ori-

gin of pearls based on differences in manganese content. Freshwater

mussel shells and pearls contain considerably more manganese than saltwater shells and pearls. Therefore， they show bright fluorescence

when ex.posed to X-rays. Phosphorescence shows after the X-ray source

is turned off. Natural saltwater pearls usually don't fluoresce. In the case

of cultured saltwater pearls， the bead nucleus fluoresces through the

(non-fluorescent) nacre， provided the nacre is not too thick. Since natu-

ral and clIltl.lred saltwater pearls with thick nacre cannot be separated by this method， slrllctural information obtained from X-ray radiography is

requiJ'ed for identification.

While not conclusive， the following tests might provide an indication as

to whether a pearl is cultured.

• Examine the drill-hole using magnification and strong light. The brown conchiolin layer might be visible between the shell nucleus and the outer

nacreous layers of a cultured pearl. However， the absence of a visible conchiolin layer doesn 't indicate the pearl is natural.

• Direct a bright， concentrated light source through the pearls. Bead-nucle-ated cultured pearls might show the parallel layers that make up the

bead. This feature can be seen only in bead-nucleated cultured pearls

with thin nacre. Natural pearls and tissue-nucleated cultured pearls typi・

cally show only a decrease in light transmission from the outer edges to

the center. This test is not infallible: Many bead-nucleated cuLtured pearls don 't show parallellines， and cracks in natural pearls or tissue-nucleated cultured pearls can cause a striped appearance.

• To separate cultured freshwater pearls from natural pearls， they must be X-rayed and the structure must be examined carefully.

It requires a trained and experienced eye to interpret the results. Dental

and medical X-ray equipment uses settings and exposures that don't pro-duce adequate results for identifying pearls. If in doubt， submit pearls to the GIA Gem Trade Laboratory for identification.

Identifying Imitation Pearls Imitation pearls are manufactured to simulate both saltwater and freshwater

pearls. They can be made from glass， plastic， wax， or shell， and coated with various products to mimic the appearance of natural and cultured pearls.

• The tooth test. Gently rub the bead across the biting edge of your front teeth. Imitation pearls will feel smooth; natural and cultured pearls feel

gritty. Caution: coated natural and cultured pearls can also feel smooth.

• Examine the surface using magnification. The texture of imitation pearls can look smooth and even when compared to cultured pearls.

CARE AND CLEANING Pearls are more delicate than most gem materials， so they require special care. Store pearls in a soft pouch or separate container to minimize contact

with other jewelry.

• Clean pearls regularly with a soft， damp cloth or lambskin chamois.

• Periodically clean pearls in a solution of w紅 mwater and non-detergent soap; lay pearls on a clean towel and dry completely before wearing.

• Periodically restring strands of pearls. The silk string should be clean，

the knots should be tight， and there should be no slack between the knots

and pearls.

• Never ultrasonic or steam-clean pearls.

• Use only commercialjewelry cleaners that are made specifically for pearls.

Caution your customers to remove pearl jewelry before they:

• Apply cosmetics， perfume， or hair spray

• Swim in chlorinated pools

• Wash dishes， do housework， or do gardening

• Do strenuous work or exercise

P ~^RI 1I1senll'IION SVSTEM M NtJ1

In this X-ray of cultured pearls you can see that the bead nucleus is more dis-tinct than the surrounding nacre.

Compare this X-ray of tissue-nucleated cultured pearls to the bead-nucleated pearls in the photo above. As you can see here， there is no demarcation between the bead nucleus and the nacre. Tissue-nucleated pearls are virtually all nacre.

23

[iIA I'FARI L.BAOING

SHAPE COLOR The three main categories of shape a陀 spherical，sym- The overall color of a pearl is called bodycolor. This metrical， and baroque. The seven standard shαpes fall bodycolor can have overlying translucent color( s) within one cαtegoηor another. P.巴αrlsnot falling into called overtone. Orient， a suヴαceiridescence， can be these groupings are described as they appear. For present as well. Pearls can be treated to enhance their example， bar or cross. The shαpe of a pearl can be mod- color and/or overtone. Common treatments include dye，

ified by the p陀 senceof circles. imαdiation，αnd coating. Note: Red is referred toαs Pink when describing bodycolor in pearls.

Round Semi-baroque Bodycolor Tone

Pearl(s) appe紅 round.No Pearl(s) appear not quite Neutrals See Pearl Color Vぽiationsare app紅entto symmetrical; off-round White Terminology Grid on

the unaided eye. and/or slightly irregular Gray Pages 14 and 15， and drop， button， or oval Black Color Reference Charts.

Near-round shape. Near-neutrals

Pearl(s) slightly elongated Silver Saturation

or flattened. Only minor Baroque Cream See Pearl Color vanatlOns紅'eapparent to Pearl(s) appearωhave Brown Terminology Grid on

the unaided eye. no apparent symmetry; E盟 E

Pages 14 and 15， and irregular in shape. Color Reference Charts.

Oval Red (Pink)

' Orangy Red (Orangy Pink) Pearl(s) appear symmetri- Other Reddish Orange (Pinkish Overtone

cal， rounded & oblong. Any norトstandardshape. Orange) Rose

' For example: bar， cross， Orange Green

Button cozn. Yellowish Orange Blue

Pearl(s) appear symmetri-Orangy Yellow Other: Note the color

Circled IModifier) Yellow present. cal， rounded & flattened.

Greenish Yellow None: No notation One or more grooved or

Yellowish Green necessaη.

Drop ridged rings around the Green

Pearl(s) appear symmet-circumference of any

Bluish Green Orient shape pe紅l.If由egrooves 、rical， rounded & pear Blue Green a

extend around the entire . Note the presence if shaped. Green Blue '

circumference of the ' seen on the majority of Greenish Blue

pearl， describe it as a c廿ー pearls in a strand. Blue

cled pearl. Use the shape Violet

category and the circled Purple

a Common Treatments

modifier. For example: Reddish Purple (Pinkish Dyeing

Circled oval. Purple) Irradiation

Purplish Red (Purplish Coating

Pink)

J"

24

巴.

pI-AHL Ol:Sr:HIf'11臼N SYSTF 町内 MANIIAI

LUSTER SURFACE QUALlTY NACRE QUALlTY MATCHING Luster is the intensity There are many types ofchar- Nacre quality is related to Matching describes the uni-

of light reflected from α'Cteristics and/or irregulari- durabiliり)and luster. lf the formity of pearls in jewelry. the SUIプαceof the pearl. ties usually confined to the nacre is too thin， the nucle- lt's judged by the consisten-

There are four cate- pearl's suゆce.These can us might be visible. Thick 句 ofsize， shape， color; lus-

gories of luster. αiffect appearance or durabil- nacre doesn 't gωrantee a ter， suiface quality，αnd ity or both. 如何凶appearance.G如 s砂 nacre qualiか'.For pearls

nacre伊 'f1lityin three D仰ー that a陀 intentionallymis-

gones. matched， look for a加rmo-

nious design and balanced

effect.

Excellent (E) Clean (CL) Acceptable (A) Excellent (E)

Reflections appear Pearl(s) might have Nucleus is not noticeable. 恥10stto all pearls have a

bright and sha中・ minute surface character- Appearance is not chalky. uniform appearance and istics that are difficult to are drilled on-center.

Good (G) see. If pearl(s) appear Nucleus Visible (NV)

Reflections are bright absolutely free from

Strong blinking when Good (G) blemishes to the unaided

but not sha中・ eye， add the designation pearl(s) are rotated. The Most to all pearls have

Spotless nucleus is evident. only minor variations in

Fair (F) uniformity.

Reflections are weak and Lightly Blemished (LB) Chalky Appearance (CA)

blurred. Pearl(s) have only minor Obvious dull appearance. Fair (F)

surface irregularities visi-Most to all pearls have

Poor (P) ble. noticeable variations in

Reflections are dim and uniformity.

diffused. Moderately Blemished Not Applicable (N/A)

(MB) Note N/A when describ-

Pearl(s) have noticeable ing single pearls.

surface characteristics.

Heavily Blemished (HB) For pearls that are inten-tionally mismatched， look

Pearl(s) have obvious for harmonious design surface irregularities that and balanced effect. might a百'ectdurability.

25

PEARL INDUSTRV ASSOCIATIONS There are several pearl industry organizations that provide product information and marketing materials to the

wholesale and retail jewelry trade. For additional information about their services， contact the following:

Devin Macnow

Cult町edPearllnlormation Center

321 East 53rd Street

New York， NY 10022

Phone: 212-688-5580

Fax: 212-688-5857

Web site: http://www.pearlinfo.com

Devin Macnow， Regional Director， USA

S曲目thSea Pearl Consortium

321 East 53rd Street

New York， NY 10022

Phone: 212-688-2420

Fax: 212-688-5857

Email: maxyo@ibm.net

Web site: http://www.sspc.netl

Japan Pearl Exporters' Ass目ciation(JPEA)

Pearl Center Building

6・15Kyobashi 3-Chome， Chuo-Ku

Tokyo 104， Japan

3-3561-7807

3・3561-7809

26

Japan Pearl Exporters' Association (JPEA)

Japan Pearl Center Building

122 Higashi・Machi，Chuo・Ku

Kobe 650， Japan

78-331-4341

78-331-4345

Perles de Tahiti G.I.E.

P. O. Box 20470

Papeete， Tahiti

French Polynesia

Phone: 689-45-03-03

Fax: 689-45-04-50

Web site: http://www.tahiti-blackpearls.com

Pearl Grading Worksheet

Name

Item No. Pearl Type

Size

Shape R一一 NR Ov Bu D SB

Other

Color

Bodycolor

Overtone

Orient Yes No

Evidence of Treatment Yes No U ndetermined

Luster E G F

Surface Ouality CL LB 民1B

Nacre Ouality A NV CA

Matching E G F

Comments:

。Copyright2000 Gemological Institute of America

P FARI OF又仁RIPTlOru又YSTFM MA~!l IAI

Date / /

B

P

HB

N/A

27