Everything you need to know about Pearls

Let's start by saying what pearls are, a "living" jewel, or rather a natural product, spontaneous or cultivated by man, rare and precious which has always been embellished in jewellery, to enhance the beauty of the women or men who wear them.

more technically, pearls are "a concretioned product with an essentially carbonate composition, generated within specific molluscs, by reaction to the presence of a foreign body in the organism, therefore considered biogenic material". Pearls are therefore of organic origin, formed in fresh or salt water molluscs.

The pearl is a body without sharp edges, made up of crystalline layers of calcium carbonate (essentially aragonite), superimposed in imbrices, concentric and caged in a three-dimensional network of shells.

well now that we know "technically" what pearls are, we know how they came to us, how the techniques have been handed down over the years to obtain increasingly beautiful and rare pearls....

in reality the term pearls is much more recent than you think, the Greeks and Romans were not aware of this term, they commonly called them "margarita". Pliny the Elder called Perna a mollusc from the Black Sea, while only in the Middle Ages did the popular term pearl emerge, probably deriving from pirula or perula (small pear), or from the Latin "spherula" (small sphere).

the oldest history text that mentions pearls dates back to 2500 BC, although it is said that there was a large trade in pearls in India, the first pearls mentioned in a historical text only date back to the 2nd century. AD, when the Gulf of Mannar (Sri Lanka) was first mentioned as "the place where pearls are found".

The Persians were also among the first to use pearls, especially among the royals, as mystical-ornamental objects, such as the string of Persian pearls found in 1901, and exhibited at the Louvre museum in Paris, a string of 216 pearls, found in Susa in the winter palace of the kings, which dates back to the 5th - 6th century. B.C

In Italy, as in some other countries of the old continent, various stories are told about pearls, some of these linked to superstition. In fact, it is said that they are a drop of dew that fell inside a shell. If you want to donate them to someone, you should give them in an even number and have them repaid with a coin as a superstitious gesture. even if many do not believe these stories, in fact it is also said in Italy that pearls are the greatest sign of love and passion, in China of wisdom and power, in Japan of purity and sincerity, wherever you go, stories you find. ..

But where are pearls formed? and how are molluscs made?

Pearls are formed inside molluscs, let's see how they are formed and how pearls are formed specifically.

Structure of a mollusc:

1) outermost layer, i.e. PE shell or periostracum - made up of conchiolin, a nitrogenous polysaccharide, rigid organic material similar to the chitinous integument of insects. Conchiolin is opaque and insoluble in water, alcohol and ether.

2) ostracum OS - is made up of hexagonal prisms of calcite, arranged perpendicularly to the layers of conchiolin, a substance that acts as a glue.

3) hypostracum IP - is made up of calcium carbonate, in the form of aragonite in which regularly arranged crystals are immersed in the conchiolin which always acts as a glue. the hypostracus is commonly referred to as "MOTHER OF PEARL"

4) outer mantle\epithelium EE - made up of epithelial cells which are directly in contact with the shell and which secrete nacre (conchiolin and calcium carbonate). - NB : "the mantle or pallium is a skin flap located between the shell and body of the animal. It is made up of three states 1) external epithelium, 2) connective tissue and 3) internal epithelium."

4\2) connective tissue TC - the intermediate muscular part made up of smooth unicellular fibres, often branched and united in a tissue which sometimes has a cartilaginous consistency.

4\3) internal epithelium EI, visceral sac, gills - is formed by epithelial cells that replace the animal's respiratory system.

5 foot

6 kidneys

7 heart

finally the "zipper" in the case of molluscs protected by two shells instead of a single one, is the part that holds the two parts of the animal's shell together.

Further information :

The species of mollusc can be identified by the imprint it leaves internally.

exactly the mollusc phylum is the second largest in the animal kingdom.

approximately 110,000 species of molluscs are known, including seas, fresh waters and land.

pearls should never be put in contact with sea water as it would dehydrate the pearl inside, even if they are born in the sea they never come into contact with sea water.

perfumes and sweat also contribute significantly to the degradation of the pearl.

but the molluscs that interest us are the soft-bodied pearl-bearing ones, and are divided into three large classes:

1) LAMELLIBRANCHI OR BIVALVES

2) GASTERPODS

3) CEPHALOPODS

the common characteristic is that they have a soft body protected by a single shell or by two or more shells called bivalves.

they differentiate into the three groups based on their mode of locomotion, and the type and shape of the shell.

How are pearls formed?

the presence of a foreign body inside the pearly mollusc, which penetrates through the various layers of the mollusc, coming into contact between the shell and the mantle, passing through the various internal layers of the mollusc such as the periostracum, ostracum, hypostracum, for the mollusc it snaps a form of defense for itself, by reaching the foreign body up to the connective tissue, the mollusk tends to isolate it by covering it with layers of calcium carbonate and conchiolin, i.e. the perlagione and the nacre, and the final result will be a pearl.

the final crystalline structure that forms of aragonite crystals is typical and significantly influences the particular optical effects of reflection, refraction, interference and diffusion which together constitute the Orient, a very important phenomenon for the evaluation and distinction of the quality of pearls.

pearls are of natural origin, both spontaneous and cultivated, if produced by a living mollusc, the difference greatly affects their rarity and commercial value.

spontaneous pearls are usually formed due to the fact that foreign bodies such as parasites or larvae penetrate the mollusc or, much more rarely, fragments of the shell of the same mollusc or grains of very fine sand end up inside the mollusc. These are really very rare and in those cases also very expensive if of good quality.

For cultured pearls, however, these are all those pearls that are formed thanks to the intervention of man who, by operating the mollusc with a scalpel, grafts, inserts, a nucleus (usually of mother-of-pearl but also of other materials) thus doing cover the latter from the mollusc with conchiolina and aragonite, and obtain the pearls. the mollusk can reject the nucleus several times following the operation.

the times to obtain a pearl of medium-fair size range from a minimum of 6 months to more than 3 years, the mortality percentages due to hurricanes and storm surges are very high, which is why to obtain a string of excellent quality calibrated pearls we it can take decades, and this is also due to their very high cost, in addition to the costs of raising and caring for them as they are living beings and get sick like anyone else. not to mention the research costs to obtain ever better material. usually from each mollusc you get from 1 to a maximum of 3 pearls of jewelery size and quality, so this also has a significant impact on the final costs. while for some molluscs such as the keshi pearl-producing molluscs, they can produce up to 60 pearls at a time... we will go into more detail later.

But what are the molluscs that produce them called? where they live? in which seas? and above all, what characteristics do they have?

Below I present 3 simplified tables to explain the names and characteristics

1 - LAMELLIBRANCHI:

the lamellibranchs are so called due to the appearance of their gills, lamellae, they are in fact mainly marine aquatic animals.

they are also known as bivalves, because their shell is divided into two parts, joined by the hinge. their body is bilateral and symmetrical, covered by a mantle that leaves some orifices open which represent anal and gill siphons.

up to 20,000 species are known, mostly from the Pteridaea family.

the characteristics to be observed most, which are important for the distinction of molluscs, are: the habitat in which it is found, the maximum dimensions of the valves and the color of the mother-of-pearl.

the species shown below are those that produce pearls.

CLASS	FAMILY	TYPE	SPECIES	SIZE DIAM. MAX MOLLUSC	LIP COLOR	TRAINING PLACE	PEARL COLOR	AVERAGE PEARL DIAMETER	ORIENT
LAMELLIBRANCHI	PTERIIDAE	PINCTADA (or pteria)	MAXIMA	30 CM	GOLDEN - BLACK - SILVER (only cultivated)	AUSTRALIA - PHILIPPINES	GOLD - BLACK - SILVER	UP TO 17\19MM	YES
			MARGARITIFERA (CUMINGI)	20\25 MAX 30 CM	BLACK	SOUTH SEAS (Red Sea, Australia, Polynesia..)	BLACK - BLACK\SILVER	UP TO 15\17MM	YES
			FUCATA MARTENSI (AKOYA)	15 CM	WHITE - PINK	JAPAN (Pacific coast)	WHITE\PINK - WHITE\BLUE	UP TO MAX 13MM	YES
			MAZATLANTICA "pearls of Cortez"	20 CM	BROWN - GREYISH	PACIFIC OCEAN (Bay of California, up to Peru)	BLACK BASE - IRIDESCENT SHADES	13-15 MM	YES
			STERN	13 CM	"RAINBOW" LIGHT GRAY WITH IRIDESCENCES	PACIFIC OCEAN (Bay of California, up to Peru)	BLACK WITH PURPLE GREEN PINK BLUE IRIDESCENCES	13 - 15 MM	YES
			RADIATE	8 CM	ALMOST ENTIRELY WHITE	SRI LANKA	WHITE - CREAM - SILVER GRAY - YELLOW	LESS THAN 2MM	YES
			PENGUIN "penguin wing"	D 20 TO 30 CM	ROSE	INDO - PACIFIC	WHITE\PINK	13 MM	YES
	PINNIDAE	FIN	NOBILIS "castanet"	65 CM	SHINING BROWN	MEDITERRANEAN SEA	BROWN - WHITE1GREY - ORANGE - REDDISH UNTIL THE 20TH CENTURY	RISK OF EXTINCTION - CAUSE POLLUTION	NO
	TRIDACNIDAE	TRIDACNA	GIGAS	1.5 MT 300 KG	WHITE	MALAYSIA - INDONESIA - AUSTRALIA	"CLAM PEARL" WHITE	GIANTS - RISK OF VULNERABILITY	NO
	TAXONOMY	PLACUNIDAE	PLACUNA PLACENTA	15 CM	WHITE	GULF OF ADEN, PHILIPPINES	WHITE - EDIBLE MOLLUSC	UP TO 4\5 MM SMALL SIZES	NO
	PECTINOIDEA	PECTINOIDAE	PECTEN	12-14 CM	REDISH ORANGE	CENTRAL AMERICA - LOWER CALIFORNIA	SCALLOP PEARLS SPOTTED COLOR DEPENDING ON THE COLOR OF THE SHELL - FROM ARNACIOUS TO RED STRIPED - EDIBLE MOLLUSC	UP TO 40 CT - VERY LARGE AND OF VARIOUS IRREGULAR SHAPES	NO
	MYTILIDAE	MYTILUS	MYTILUS EDULIS "MUZZLE"	5 - 10 CM	WHITE \ GIRGIO - LIGHT BLUE - DARK BLUE	NORTH ATLANTIC - MEDITERRANEAN SEA - NORTH PACIFIC	GRAYISH WHITE - PURPLE - BLUE - BLACK WITH SHADES OF BLUE	SMALL A FEW MM	NO
	VENERIDEA	MERCENARY	MERCENARY MERCENARY "CLAMM"	3 - 5 CM	PALE WHITE WITH PURPLE SHADES	NORTH AMERICAN ATLANTIC FROM CANADA TO GEORIGIA - EDITERRANEAN AND ADRIATIC SEA - EASTERN ATLANTIC MOROCCO - BRITISH ISLANDS	WHITE - DARK PURPLE - PINK PURPLE - BROWN	SMALL A FEW MM	NO

2 - GASTEROPODS:

approximately 80,000 different species are known, they are characterized by an asymmetric body surrounded by a single dorsal shell, rolled into a spiral. their movement is due to their locomotor organ called "foot". they often have an operculum or "cap" to close the valve.

the species shown below are those that occasionally produce pearls.

CLASS	FAMILY	TYPE	SPECIES	SIZE DIAM. MAX MOLLUSC	SHELL COLOR	TRAINING PLACE	PEARL COLOR	AVERAGE PEARL DIAMETER	ORIENT
GASTEROPODS	STROMBOIDAE	LOBATUS (Strombus)	GIGAS	30 CM AND UP TO 3 KG IN WEIGHT	it produces calcareous, non-nacreous concretions, TYPICALLY PINK, ORANGE-PINK	CARIBBEAN INDIAN OCEAN, (mainly sought for food purposes)	produces the famous CONCH PEARL, or STROMNUS PEARLS, typical flaming, oval shape	3 MM ON AVERAGE	NO
	VOLUTIDAE	APPLE TREE	APPLE TREE (Volutes	FROM 17 TO 27 CM	BROWN-ORANGE, ORANGE, CREAM	VIETNAM, MYANMAR, CHINA AND PHILIPPINES	ORANGE-BROWN TO VIOLET WHITE STRIPED	5 - 8 MM	NO
	VOLUTIDAE	APPLE TREE	APPLE TREE amphora	FROM 30 TO 50 CM	BROWN-ORANGE, ORANGE, CREAM	NORTH\EAST AUSTRALIA	ORANGE-BROWN TO VIOLET WHITE STRIPED	FROM 8 TO 30 MM, MASS FROM 5.55 ct to 201.25 ct (the largest found was 232.54 ct)	NO
	HALIOTIDAE	HALIOTIS	GIGANTEA	FROM 8 TO 20 CM	IRIDESCENT RAINBOW WITH PREVALENCE OF BLUE PURPLE GREEN YELLOW AND PINK	JAPAN, KOREA, NEW ZEALAND, AUSTRALIA AND USA	VERY DIFFICULT TO PRODUCE PEARLS, FOR NOW ONLY BLISTER AND MABé	-	-
	TURBINIDAE	TURBO	PHETOLATUS	MAX 10 CM	ZONES FROM GREEN, GREEN-BROWN, BROWN,	TROPICAL SEAS OF THE PACIFIC OCEAN	NO PEARLS PRODUCED BY TURBO ARE KNOWN, but due to its OPERCUM, with zoning that resembles an eye, it is nicknamed "St. Lucia's eye", the so-called Maona pearls are actually its OPERCUM	-	-
	TORCHIDAE	TROCHUS		10 CM	WHITE WITH IRIDESCENCES - IT DEPENDS ON THE AREA, EACH HAS ITS TYPICAL COLOR	FROM THE INDIAN OCEAN TO SOUTH EAST ASIA TO THE SOUTH PACIFIC - VERY WIDESPREAD	IT DOES NOT PRODUCE ANY - ITS MOTHER OF PEARL IS USEFUL TO CREATE CORE	-	-

3) CEPHALOPODS:

they are the most advanced and specialized ones, they do not have a high number of different species, the best known were the Ammonites, of notable importance among the Nautilodeans, which appeared for the first time already in the Cambrian period.

they are composed of an external spiral shell, divided into chambers, their organ of locomotion is adherent to the substrate, which has been transformed partly into a siphon for water irrigation of the gills and propulsion by expulsion of water, partly instead into tentacles with or without suction cups.

CLASS	FAMILY	TYPE	SPECIES	SIZE DIAM. MAX MOLLUSC	SHELL COLOR	TRAINING PLACE	PEARL COLOR	AVERAGE PEARL DIAMETER	ORIENT
CEPHALOPODS	NAUTILIDAE	NAUTILUS	POMPILIUS	20 CM	LIGHT WHITE\ CREAM WITH RED VEINS	FROM FIJI ISLANDS TO NEW GUINEA	CREAM COLORED MOTHER OF PEARL - PEARLS ARE VERY RARE, EXCEPTIONAL IF SPHERICAL WITH A FLAMED STRUCTURE, CREAM WHITE COLOR	-	-

CULTURED PEARLS:

"With the term cultured pearls we mean a concretioned product with a carbonate composition generated within mollusc centres, following human intervention, (direct or indirect), in the vital parts of the organism."

the most important name in pearl culture is certainly that of Kokichi Mikimoto, who dedicated his life to the study and developed the method of cultivating pearls by grafting. He was the first pearl trader as we understand it today, also helping many women with their working and economic position, hiring them to manage the first cultivations, and then helping them grow and training them, giving women a better social position. his successes allowed the Japanese to establish a hegemony that continues today.

in 1888 Mikimoto developed the first pearl mollusc farm. in 1893 the first 5 semi-spherical cultured pearls were produced, effectively starting cultivation as we understand it today. in 1896 he obtained the first patent under the name "pearl foundation". However, in 1093 his employees, the carpenter Tatsuhei Mise, and in 1907 the zoologist Tokichi Nishikawa, obtained perfectly spherical pearls.

the two reached a compromise in 1908, filing a patent that involved the grafting of a spherical nucleus of mother-of-pearl and a fragment of epithelial tissue, a patent that is still in use today. Mikimoto then purchased the rights, developing it in his laboratories, until it was refined to its best.

after having had commercial problems due to the difficult distinction between a cultured pearl and a spontaneous one, at the time they developed fast methods for their distinction and from which moment the production and marketing of cultured pearls gained a great foothold in the world.

TYPE OF CULTURED PEARLS

1) TRADITIONAL SPHERICAL: these are all those pearls produced by grafting a spherical nucleus of mother-of-pearl inside the mollusc, in the reproductive part.

2) BLISTER: They are produced from molluscs that have already been grafted, such as Pinctada maxima, margaritifera, margaritifera cumingi, or from freshwater Haliotis or even from Hyriopsis cumingi.

production occurs at the limit of the production cycle, or if a mollusc has already rejected the nucleus graft several times, not wanting to accept it in any way to produce pearls.

a generally 3\4 spherical core is fixed between the shell and the mantle which are subsequently put back into the sea.

usually a fair thickness is achieved in 2 years, then it is removed and polished in the portion remaining in contact with the shell.

they generally range from 10 to over 20 mm. the farms that produce them are in the Philippines, under the guidance of Japanese technicians.

3) KESHI:

They are pearls without a nucleus that are formed accidentally by man in a certain mollusc that has already been grafted, the term "keshi" means poppy seed in Japanese, and these can only form if the following conditions exist:

1 - the mollusk has rejected the nucleus, and the fragment of epithelium remains inside, covering it, giving life to the pearls called "without nucleus"

2 - some cells of the epithelial tissue inserted together with the nacre nucleus detach and end up in the gonads, proliferating and stimulating the production of irregular pearls

3 - the fragment of epithelial tissue has not been inserted well into contact with the nucleus, therefore it forms an independent pearly sac, in which other pearly material develops.

4) MAB IS:

Mabé pearls are a composite material, for which P. maxima margaritifera, cumingi, P. penguin and large haliotis are used, at the limit of their reproductive cycle, as this technique leads to irreparable damage to the shell. the best known is made up of 4 parts:

1 thin layer of convex shaped pearlescent

2 mother-of-pearl internal body

3 glue

4 mother of pearl.

dimensions usually range from a diameter of 13 to 16 mm.

"osmena" pearls are mabè obtained from the curved part of the shell of the Nautilus mollusc.

Cores:

traditional mother-of-pearl nuclei are made from the mother-of-pearl of these 3 molluscs, in addition to the fragment of epithelial tissue:

1 Pleurobema cordatum (freshwater mollusc)

2 lamprotula leai (freshwater mollusc)

3 trochus (marine gastropod)

To be grafted, the molluscs must have reached at least a minimum diameter of 7 cm during cultivation times, pinctada fucata martensi must have reached at least 3 years of life and 15 cm in diameter. the molluscs are taken from the water and selected in the shortest possible time. after their grafting they must remain in tanks, in baskets in groups of 10 for at least 6 weeks under observation, before being put back into the sea. the molluscs that survive are then moved to other baskets, which are then fixed to the rafts in the sea, from 5 to 15 baskets are fixed to each raft, for a maximum of 180 molluscs. Molluscs with internal temperatures of 13°C slow down their growth, if the temperature drops below 8°C for a prolonged time they can even die, the optimal temperature for the growth of the mollusc and therefore of pearls is between 23 and 30 degrees .

on average each operator grafts from 300 to 1000 nuclei per day. these are carried out in spring when the molluscs are brought back to the bays from the winter resting areas.

In the end, after a period ranging from 6 to 36 months, sometimes even longer, in the winter period in which they are harvested, only 40% of the harvest is commercially exploitable, and only 5% is of excellent quality.

Pearl Rating:

the general evaluation is based on 6 factors, but a complete, serious and in-depth commercial evaluation is only possible on the basis of considerable professional experience.

what must be denoted for the evaluation is the following:

1 Dimensions

2 Form

3 Color and degree of homogeneity

4 Surface appearance

5 East

6 Thickness of the pearling

1) Dimensions:

they are measured in millimeters in the case of spherical pearls only one dimension will be indicated, in the case of pearls with different shapes the minimum and maximum size will be indicated.

furthermore, the pearl is weighed in carats, for lots technically specific terms are used such as Mommè = 3.75gr = 18.75ct (1 ct is 1/5 of a g), Kan = 1000 Mommè, in the past the term was also used grain = 0.25ct, today carats are used to specify the weight.

2) Shape:

there are all types, to summarize the most used terminologies, we will use the following table:

FORM	MODIFICATION
SPHERICAL	HALF PEARL
	3/4 (D QUARTERS)
	4/5 (FOUR FIFTH)
	SUBSPHERIC
	RINGED (ALSO POSSIBLE ON OTHER SHAPES)
OTHER FORMS
SUBSPHERIC
OVALOID
BUTTON
DROP
IN PERA
TWIN
FANTASY
SEMI BAROQUE
BAROQUE

3) Color and shade:

the color of a pearl is defined by its base color and shade.

the base color is observed along the circumference or in any case, near the perimeter area.

the shade instead is observed in the center of the area in which the light is reflected.

For color evaluation it is possible to refer to a general color scale.

AKOYA CULTURED PEARLS
BASIC COLORS	SUMATURE
WHITE	ROSE
CREAM	GREEN
YELLOW
ROSE
BLUE

4) Surface appearance:

this aspect is defined without the aid of microscopes or magnifying glasses, but must be carried out with the naked eye.

the scale of values ​​to indicate is:

1 regular

2 slightly irregular

3 irregular

4 very irregular

these vestments are used both to evaluate a single pearl and a string of pearls.

5) Luster and orient:

the term orient was coined to describe Japanese Akoya pearls, for their particular, suffused and velvety appearance, with micro flashes of iridescent color moving on the surface.

scientifically, the orient is a set of optical effects such as: dispersion, reflection, refraction, interference and diffusion of light.

the scale of values ​​to describe the east is as follows:

1 excellent

2 good

3 discreet

4 poor

6) Degree of homogeneity:

the degree of homogeneity is evaluated in the threads by considering the pearls that make up the thread as a whole.

is evaluated with the following scale:

1 voucher

2 discreet

3 poor

7) Pearl thickness:

the thickness of the pearl is evaluated in the case of pearls drilled through or only on one side with the aid of a 10x lens or under the microscope, in the direction of the hole. this thickness is evaluated according to the following scale:

1 thick

2 medium

3 thin

4 insufficient

if the pearl is not perforated the only way to establish the thickness of the pearl is to carry out a radiographic or xerographic examination.

this general framework aims to give those interested the opportunity to delve deeper into a very broad and decidedly interesting topic, both from a commercial and animal point of view.

see you soon with other articles 😉