Glossary

abalone blister pearls

half-nacreous natural pearls formed inside an abalone shell.

baroque

a pearl shape that is irregular and not symmetrical.

calcite

together with aragonite and conchiolin, this crystalline form of natural calcium carbonate make up the structure of nacre.

drop

taking its name from a water drop or teardrop, this refers to a symmetrical pearl shape that’s round on one end and tapers almost to a point on the other.

endoscope method

method of testing whether a pearl is natural or cultured.

faceted cultured pearls

pearls carved to create rhombic or triangular surface shapes and yield a sparkling optical effect when the wearer moves.

gastropod

univalve mollusks with heads and eyes, including land and sea snails.

half-drilled pearls

pearls drilled to 2/3 or 3/4 of their diameter for setting in pearl jewelry.

nacre

ragonite and calcite platelets bound together by conchilion that completely compose bivalve and abalone natural pearls, keshi, tissue-cultured freshwater pearls, and the coating on the nucleus of bead-cultured and bead-and-tissue-cultured pearls.

opera necklace

pearl necklace measuring 28 to 35 inches (70-90 cm).

PAPPE

Philippine Association of Pearl Producers and Exporters.

quality factors

characteristics of natural or cultured pearls used to establish their value.

radial structure

calcite or aragonite crystals of a pearl’s prismatic layer are arranged in a pattern so they radiate like rays of sunlight from a central core.

saltwater pearls

natural or cultured pearls produced by a saltwater mollusk.

acid test

the use of hydrochloric acid to test the authenticity of pearls
 

adductor

the muscle that opens and closes a bivalve mollusk’s two shells

Ago Bay, Japan

home to Mikimoto’s first pearl farm, and to many akoya farms today
 

akoya

the Japanese term for the Pinctada fucata martensi mollusk

 

akoya keshi

a formation of a small pearl found in the akoya mollusk as a byproduct of the pearl culturing process

akoya pearls

cultured or natural pearls from an akoya mollusk

ama

 the historical female pearl divers of Japan who were trained to dive without scuba gear or air tanks

ama

 the historical female pearl divers of Japan who were trained to dive without scuba gear or air tanks

aragonite

calcium carbonate crystals that are a component of nacre and mother-of-pearl, and arranged in a brick-like pattern

atoll

a ring of coral that nearly encloses a lagoon, and is considered the best place to farm cultured pearls in the Pinctada margaritifera mollusk

bead-and-tissue-cultured pearls

freshwater or saltwater cultivated pearls whose growth is started by implanting a shell bead nucleus and a donor-mollusk mantle-tissue piece in the mantle, gonad, or other body part of a host mollusk

bead-cultured pearls

freshwater or saltwater cultured pearls whose growth is started by implanting a shell bead nucleus in an existing pearl sac from which a first-generation cultured pearl was removed

bivalve

a mollusk from the Bivalvia class having a two-part shell attached by a hinge

Biwa pearls

cultured freshwater pearls in Lake Biwa, Japan

black-lipped mollusk

 general name for the Pinctada margaritifera and Pinctada margaritifera cumingi mollusks

black pearls

pearls of naturally dark colors formed by the Pinctada margaritiferaPinctada margaritiferacumingiPinctada mazatlanica, and Pteria sterna mollusks

black lip oyster

common name of the Pinctada margaritifera

blemish

refers to any surface defect on a pearl, such as cracks, chips, dull spots, wrinkles, spots, holes, bumps, and pits

blister pearls

pearls attached to the shell of the host mollusk

body color

the aspect of a pearl’s color that is triggered by pigment as conflicting to light interference

bu

 historical Japanese linear measure to designate the diameter of a bead nucleus (bu = 3.03 mm)

buoys

 used to drift lines from which mollusks are dangled in net panels or any other holding devices

byssus

 a group of thread-like tissue that bivalve mollusks use to anchor themselves to a solid external surface

calcium carbonate

 what pearls are mainly composed of

candling

a process on examining a pearl in front of a focused light source to check if it shows the layered structure that proves it contains a bead nucleus

carat

a weight measure used for natural pearls

cherry

 a reddish overtone found on pearls produced by Pinctada margaritifera

choker necklace

 a necklace that lie above the collar bone, and is 14 to 16 inches in length

CIBJO

 The Confédération Internationale de la Bijouterie, Joaillerie et Orfèvrerie is also known as the World Jewellery Confederation, an international confederation of jewelry, gemstone, horology, and silverware trade organizations

circled pearls

 pearls with raised concentric rings around its surface

clam pearls

 non-nacreous pearls found in clams

coin pearls

 coin-shaped bead-and-tissue-cultured pearls

collar necklace

a necklace measuring 10 to 13 inches (25 to 33 cm)

concentric structure

the layering of calcium carbonate crystals that is characteristic of natural pearls, tissue-cultured pearls, bead-cultured pearls, and the nacre layer of bead-and-tissue-cultured pearls

conch pearls

 non-nacreous pearls formed by the conch shell

conchiolin

the organic element that acts like glue and binds crystals together

Cortez pearls

 trade name for Pteria sterna in the Gulf of California, which is also called the Sea of Cortez

cultured pearls

pearls produced by the human insertion of a bead in a freshwater mussel or saltwater mollusk

epithelial cells

cells on the shell side of a mollusk’s mantle tissue produce mother-of-pearl and nacre

epithelial graft tissue

piece of mantle tissue from a donor mollusk rooted with a mother-of-pearl bead in the gonad or other body part of a host mollusk to produce a cultured pearl

epithelium

this covers the mantle of the pearl, protecting the surface that may come into contact with foreign substances

first-generation cultured pearls

 freshwater or saltwater cultured pearls whose growth is started by implanting a tissue piece, or a bead nucleus and tissue piece, in a host mollusk that has not grown a pearl before

flame structure

produced by aragonite crystals organized in two directions that are often intertwined

freshwater pearls

 pearls grown in mussels in a non-saline environment

gem quality

perfectly clean pearl exhibiting fine color and luster

giant clams

 also known as Tridacna gigas, they are non-nacreous natural pearl producers that are listed as a threatened species

GIA

Gemological Institute of America, nonprofit school and gemological laboratory founded in 1931

GIA pearl grading system

 grading system for cultured pearls

gold-lip mollusk

Pinctada maxima mollusk used to produce natural-colored gold South Sea pearls

gonad

the reproductive organ where a bead nucleus or nuclei and donor-mollusk tissue piece or pieces are implanted to produce cultured pearls

graduated strand

strand of pearls with 3 mm or more gradation from the ends to the middle, with the largest pearl as the center

graft tissue

donor-mollusk mantle tissue piece rooted with or without a bead nucleus in a host mollusk to produce a cultured pearl

graft

 the process of inserting a piece of graft tissue with or without a bead nucleus in a host mollusk to induce the production of a cultured pearl

grain

 unit of weight associated with natural pearls

half-round nucleus

nucleus used to produce cultured blister pearls

hama-age

 newly harvested cultured akoya pearls in Japan

hama-age auctions

 annual auctions of newly harvested cultured akoya pearls in Japan

hanadama

highest quality portion of a cultured akoya pearl harvest; often used for rings or earrings

hardness

 pearls range from 3.5 to 4.5 on the Mohs hardness scale

harvest

removing cultured pearls from mollusks on a pearl farm

hue

first impression of a pearl’s color

hypostracum

 mother-of-pearl layer of a pearl-bearing bivalve mollusk shell, the shell layer adjacent to the mantle

Hyriopsis cumingi

a triangle shell mussel native to China, being used extensively in cultured freshwater pearl production

Hyriopsis schlegeli

a Biwa pearly mussel native to Japan used to produce tissue-cultured freshwater pearls in Lake Biwa

ikecho-gai

 Japanese name for the Biwa pearly mussel, Hyriosis schlegeli

interference

 creates the iridescent play of color on the surface of a pearl; refraction, diffraction, and thin-film interference occur as light penetrates extremely thin nacre layer

iridescence

 play of color over the surface of a pearl as interference divides white light into its component colors, caused by the overlapping of successive layers

irritant

a minute snail, worm, fish, crab or any other small particle that begins the formation of the pearl

kan

a Japanese scale unit used to measure pearls (1 Kan = 1,000 momme)

Kasumigaura cultured pearls

 cultured pearls that grow in freshwater mussels in Japan’s Lake

keshi

Japanese word for “poppyseed”; these are small natural or cultured pearls

Keshi pearls

pearls made by accident as a result of a pearl culturing process

Kuri Bay

 site of the first successful Australian South Sea pearl farm, founded in 1956 in remote Western Australia, named for Tokuichi Kuribayashi, president of Japan’s Nippo Pearl Company

Lake Biwa

 location of Japan’s first freshwater pearl culture operations

Lake Kasumigaura

 located northeast of Tokyo, Lake Kasumigaura is Japan’s second largest freshwater lake and origin of Kasumigaura (Kasumi, Kasumiga) pearls

lantern baskets

baskets used to hold young mollusks when suspended from lines during saltwater pearl culture

longline systems

horizontal lines stretched between buoys and anchored to the bottom at both ends while Chaplets (vertical lines) with baskets or net panels of nucleated mollusks are suspended underwater from the longlines

luster

quantity and quality of light reflected from the surface or just under the surface of a natural or cultured pearl

mabe

originally, the Japanese trade term for an assembled blister pearl grown in Pteria penguin; today, the word is used to describe any assembled blister pearl

sautoir

pearl strand longer than 36 inches (90 cm)

second-generation cultured pearls

freshwater or saltwater cultured pearls whose growth is started either by implanting a shell bead nucleus in an existing pearl sac from which a first-generation cultured pearl was removed, or by letting the mollusk grow a beadless cultured pearl in an existing pearl sac from which a first-generation cultured pearl was removed

second grafts

cultured pearls grown in existing pearl sacs after the first harvest; same as second-generation cultured pearl

seed pearls

natural pearls less than 2 mm in diameter

Majorica pearls

imitation pearls created by coating a glass nucleus with essence d’orient, which is made from guanine crystals extracted from scales on the undersides of certain fish

semi-baroque pearls

off-round, asymmetrical pearls but not quite as irregular as a baroque pearls

mantle

organ lining the shell of freshwater and saltwater bivalve mollusks

mantle graft tissue

tiny piece of tissue cut from a donor mollusk’s mantle and implanted with or without a bead nucleus in a host mollusk to produce a cultured pearl

semi-round pearls

off-round pearls having a symmetrical shape or a slight deviation of symmetry

shinju

Japanese word for pearl

margarita

Greek and Latin word for pearl

silver-lip mollusk

Pinctada maxima mollusk that has silver rather than gold inner shell edges; used to culture South Sea pearls

margaritifera

genus name applied to a group of freshwater mussels, and the species name applied to the black-lip pearl mollusk

South Sea pearl

natural or cultured pearl produced by the Pinctada maxima mollusk

master set

group of pearls used for comparison to assess the quality characteristics of cultured pearls submitted for grading

spat

saltwater mollusk larva old enough to attach itself to a fixed surface

matching

matching pearls for uniformity in a strand or piece of finished jewelry

matinee length

pearl necklace measuring 20 to 24 inches (50 to 60 cm)

melo pearls

natural non-nacreous pearls found in the Melo melo marine gastropod

surface

one of the quality factors considered when grading a natural or cultured pearl

Mikimi

trade name for second or third grade Majorica imitation pearls

symmetrical pearl

exactly the same shape on both sides of a central axis

Mikimoto, Kokichi

first person to commercially produce spherical cultured pearls using the Mise-Nishikawa method of pearl culture

Tahitian cultured pearls

produced by a black-lip mollusk (Pinctada margaritifera) in French Polynesia

third-generation cultured pearl

freshwater or saltwater cultured pearl whose growth is started either by implanting a shell bead nucleus in an existing pearl sac from which a second-generation cultured pearl was removed, or by letting the mollusk grow a beadless cultured pearl in an existing pearl sac from which a second-generation cultured pearl was removed

Miyoko pearls

imitation pearls marketed in Germany in 1983

mollusk

any invertebrate from the phylum Mollusca

momme

Japanese weight unit used to valuate cultured pearls (1 momme = 3.75 grams)

third graft

cultured pearl grown in an existing pearl sac after the second harvest

mother-of-pearl

iridescent layer (principally calcium carbonate and conchiolin) lining the inner shell of some mollusk species; also called nacre when coating a bead to form a cultured pearl or composing a natural, tissue-cultured or keshi pearl

mussel

any of a number of bivalve mollusks with a brown or purplish-black shell

tissue-cultured pearls

freshwater cultured pearls whose growth is started by implanting a donor-mollusk mantle-tissue piece in a host mollusk’s mantle

nacreous

composed of nacre

tissue method

implanting a freshwater host mussel with a donor-mussel mantle-tissue piece to start the growth of a beadless cultured pearl

nacre thickness

measured in whole and decimal fractions of millimeters, the depth of the nacre layer on the bead nucleus of bead-cultured and bead-and-tissue-cultured pearls

Umbo

also called apex, a central swelling surrounded by the concentric lines decorating the shells of bivalves

Nassau pearl

historical term for conch pearl

Valve

the shell of a mollusk

natural pearls

organic gems created in a mollusk without human intervention

X-ray testing

a test made to identify a pearl is natural, cultured or imitation

nautilus pearls

natural pearls from Nautilus pompilius which are extremely rare

queen's necklace

pearl necklace measuring 31.5 inches (80 cm)

red tide

profuse hyperproduction of algae, called an algal bloom, that weakens or kills pearl-bearing mollusks by consuming most or all of the dissolved oxygen in the water and poisoning them when the algae die and putrefy

refractive index

measure of the degree that light bends when it moves from one medium to another, for example, from air into nacre; refractive index of natural and cultured pearls is 1.51 to 1.66

rope

pearl strand measuring more than 45 inches (115 cm)

round

perfectly round pearl, or one with diameters that don’t vary by more than 2 percent

non-beaded cultured pearls

cultured pearls grown without a bead nucleus

non-nacreous pearls

natural pearls lacking a nacreous surface layer

non-nucleated cultured pearls

cultured pearls grown without a bead nucleus

nucleus

bead implanted in a host mollusk, most often with a tissue piece, to become the core of a cultured pearl

orient

optical phenomenon that produces iridescent colors on the surface of some natural and cultured pearls

ostracum

central, prismatic layer of a bivalve mollusk shell

oval

natural or cultured pearls in an oval or egg shape

overtone

secondary color on the surface of a natural or cultured pearl created by nacre layers interfering with white light and splitting it into its component colors

peacock

color most often associated with pearls produced by the black-lip (Pinctada margaritifera) mollusk; it’s a dark green gray to blue gray with rosé to purple overtones

pear

drop pearl shaped like a pear

pearl

nacreous or non-nacreous calcareous concretion formed as a progressive secretion naturally and circumstantially within a mollusk

Pearl of Allah

natural pearl from the giant clam (Tridacna gigas), it is the world’s largest non-nacreous calcareous concretion, measuring 23 cm by 14 cm by 14 cm and weighing 6.37 kilograms; the pearl was found off Brooke’s Point, Palawan Island, in the Philippines on May 7, 1934

pearl powder

ground nacre, often used in medicines and cosmetics

pearl sac

grown from epithelial cells to envelop an intruder or a bead nucleus, it deposits nacre and forms a natural or cultured pearl

pearl sieves

used to sort cultured pearls by size

periostracum

outer layer of a bivalve mollusk shell, formed of conchiolin

Pinctada

mollusk genus in the family Pteriidae. It’s the most important genus in saltwater cultured pearl production

Pinctada margaritifera

the black-lip pearl mollusk; the variety Pinctada margaritifera cumingi used to produce Tahitian and Cook Islands cultured pearls

Pinctada maxima

the silver-lip or gold-lip pearl mollusk; used to produce South Sea cultured pearls

potato

oblong pearl shaped like a potato

princess necklace

pearl necklace measuring 17 to 19 inches (43 to 48 cm)

Pteria penguin

mollusk originally used to produce assembled cultured blister pearls

Pteria sterna

rainbow-lip mollusk used to culture pearls in the Gulf of California (Sea of Cortez)