Quality of Pearls | Pearl Grace of Pearl Mail Order
There are three main ways to see the quality of pearls.
The first point is to capture the quality of pearls in terms of elements. The quality of a pearl is determined by its shape, winding, scratches, luster, and color.
The second point is to identify the type of mother oyster, whether the pearl is pearl oyster cultured, white oyster, black oyster, or freshwater. The quality elements of cultured pearls are basically the same for all mollusk pearls, but the weights differ depending on the type of pearl. For Akoya pearls, for example, we are very strict about the shape, but for white pearls and black pearls, we often use circles, baroques, and other non-circular pearls. Also, freshwater pearls that are nearly nucleus-free, like other pearls, do not take into account the "curly" factor.
The third point is to distinguish the presence or absence of processing and its degree.
1.Pearl Quality Factors and Evaluation
Pearl quality is determined by five factors: shape, winding, scratches, luster, and color. Size is not a direct factor that determines the quality of pearls, but it is a major factor that determines the value and price of pearls. The actual evaluation of pearls is done at various stages of production, processing and distribution using a combination of quality and price determinants.
For example, when a farmer estimates how much to sell the pearls he or she produces, or when a processor puts a price on the pearl at an auction and wins the bid while competing with other traders, or when the processor When a trader puts a price on a pearl that has been manufactured, and when a store clerk explains a product to a customer at a retail store, pearls are always evaluated according to some sort of quality standard. There are several methods of evaluating pearls, but we will discuss the three main ones: grading, grading inspection, and pricing.
First of all, grading is done by individually evaluating the pearl's quality factors such as shape, winding, scratches, luster, and color. Grading inspections first set a certain minimum standard for quality, and judge quality based on whether or not the standard is cleared. Export inspection of pearls is done in this way and the quality is either pass or fail. And the last is pricing. This is very similar to crading, but the difference is that the evaluation result is exchanged for money. In other words, pricing translates pearl quality disparities into price disparities. What must be noted here is that quality disparity does not necessarily equal price disparity. This is because the price of pearls is greatly affected by various factors other than quality, such as production, procurement, processing costs, market demand, fashion, and exchange rates. The quality policy of each supplier also affects the price. For example, one trader puts emphasis on the appearance of pearls and highly evaluates "color" and "teri", while another trader emphasizes durability and places points on "rolling". I have. In other words, since the merchant's product policy is expressed in its evaluation, if the criteria for value judgment are different, the evaluation will naturally be different.
Finally, I would like to talk a little about the evaluation environment. The evaluation environment is when, where, and under what light the pearl is evaluated.Specifically, the evaluation of pearls is affected by the season, weather, time of day (morning, noon, evening), window orientation, presence or absence of direct sunlight, and type of lighting lamp. It is no exaggeration to say that our quality evaluation is 100% done with the naked eye, without the use of machines other than winding measurements. In order to be able to evaluate correctly under any environment,
experienced experts are assigned to this work.
Next, let's look at how pearl quality is evaluated for each element.
Pearls come in a variety of shapes, but round pearls are the most prized. This is probably because there are very few natural pearls with perfect roundness, and they were highly valued. This trend continued even after the invention of cultured pearls, and perfectly round pearls that rolled in the direction of even the slightest inclination, such as the famous “Happo Rolling”, were prized. However, when culturing pearls, even though the nucleus of the perfect circle is put into the oyster and cultivated, there are quite a few pearls that are not perfectly round. The reason for this
is that the oyster does not evenly secrete nacre on the surface of the nucleus. In particular, the longer the culturing period, the thicker the nacre layer, so the appearance rate of pearls that are not round increases. The quality of the technique used to insert the nucleus into the oyster also affects the shape of the resulting pearl.
Recently, as the proportion of so-called “thin-rolled beads”, which are round in shape but thin in mother-of-pearl, has increased, it is no longer possible to say that round ones are necessarily of high quality. For this reason, there are some traders who claim that "deformed pearls are a proof of thick winding" and that drop and baroque pearls are of good quality. Good quality drop and pear-shaped pearls were originally cultivated by putting round nuclei in shellfish, so naturally they would not be shaped like this unless the curls are thick. In particular, white butterfly pearls have a beautiful symmetrical teardrop shape called "t1" (tear drop). will be the same highest rating.
On the other hand, non-nucleated freshwater pearls can be made in various shapes depending on the shape of the piece to be inserted. The most common type is the one called “rice”, which looks like a grain of rice. Variety of shapes can be said to be one of the characteristics of freshwater pearls.
The evaluation of the shape differs slightly depending on the type of mother shell. Akoya pearls are roughly divided into round, semi-round, semi-baroque, and baroque shapes. Things other than circles are sometimes called "deformed" or "off-round". Some traders subdivide semi-baroque and baroque. As mentioned earlier, the shape is closely related to the windings of the pearl, so the evaluation cannot be done properly without considering the windings.
White butterfly pearls and black butterfly pearls are roughly classified into round, drop, button, oval, baroque, and circle. Unlike Akoya pearls, pearls are characterized by the fact that they are recognized as one form of a circle with stripes.In the case of white pearls and black pearls,
round pearls are ranked top, but at the same time, symmetrical drop pearls with good rarity values are also highly evaluated as
freshwater pearls. The evaluation of the shape is different depending on the trader, and there is no unified one. Pearls are roughly divided into round, oval, drop, button, and baroque in the same way as other pearls. distorted circle), ``egg'' (not very long oval), ``rice'' (rice grain-shaped semi-baroque), ``flat'' (oval or squashed rice) It is called variously, such as a flat shape like this). In addition to these shapes, there are also unique shapes called sticks, butterflies, twins, dragons, and crosses. These are non-nucleated freshwater pearls, but American freshwater pearls have nucleated ones, such as bar, coin, drop, oval, It is classified into shapes such as marquise.
“Maki” is the thickness of the nacre layer, and is related to the durability of pearls and the unique deep color and luster of pearls. Rolls are also related to the farming period, with more rolls thicker in two-year farming periods than in farming periods of less than one year. The nacre layer is not simply composed of one layer, but has a structure in which more than 1,000 aragonite crystals with a thickness of 0.3 to 0.8 mu are piled up in layers. You may. In this way, even if the nacre is thick, the quality of the nacre greatly affects the color, luster, durability, elasticity, and other qualities of the pearl. Not only the thickness of the layer but also the quality of the nacre should be considered.
The thickness and quality of the mother-of-pearl layer also varies depending on the type of mother oyster that produced the pearl. Akoya pearls are generally said to be thinner than white pearls and black pearls. In general, it is not possible to compare with a ruler that is only thick and thin. Each pearl has its own characteristics, and each has its own merits. Of course, it is out of the question for any kind of mother oyster's pearls that cannot satisfy the
condition, which is a major requirement for pearls.
Evaluation of pearl rolls, like other elements, is usually done with the naked eye, but it takes considerable skill to non-destructively determine the thickness and quality of the rolls with the naked eye. In some cases, instruments are used to measure the winding, and Tahiti uses X-ray equipment to inspect pearls for export and eliminate thinly wound beads. In addition to this X-ray equipment, there are also places that use ultrasound for identification.
There is no clear standard for winding, but in the case of Akoya pearls, the minimum winding thickness is 0.3 mm on one side, and those with more than 0.3 mm are further divided into three levels: thick winding, medium winding, and thin winding. If the mother-of-pearl contains a considerable amount of pigment, such as the golden color of Akoya pearls and white pearls, and the black color of black pearls, even thin pearls will look thick, so you need to be careful.There are also pearls with extremely thin nacre layers, such as 'gira', 'kyoro', and 'wink', which are formed unevenly on the surface of the nucleus
A scratch is a convex or concave irregular part that interferes with the smoothness of the pearl surface. There are two types of scratches: “natural scratches” that occur naturally during pearl culturing, and “process scratches” that occur during processing, processing, or handling after culturing.
The reason why cultured pearls develop scratches is not well understood. Perhaps it has something to do with the nature of the pieces, the technique of inserting the nucleus, the physiological state of the shellfish, the culture environment, and so on. Since it is very difficult to remove natural scratches by polishing, etc., a hole is made at or near the location of the scratch to erase the
scratch or make it less visible.
These are not scratches that are inherent to the pearl, but are secondarily caused by the processing, treatment, and handling after the pearl has been unloaded. There may be scratches like rubbed on the surface. Processing scratches that occur on the surface of the mother-of-pearl can often be removed by polishing, but those that occur inside the mother-of-pearl are almost impossible to repair. Pearls are quite soft minerals, so great care must be taken to avoid such scratches.
The evaluation of scratches is based on four points: number, type, size, and position.
(1) Number of scratches: No scratches, 1 scratch, overall scratches, etc.
In general, the evaluation decreases as the number of scratches increases.
(2) Type of scratch: Scratches on the outside of the bead or scratches on the inside. Blistering scratches are less visible than dented scratches, so the evaluation is looser. Blistering scratches include those that swell so much that the shape is deformed, those that look like worms, and those that protrude like
warts. On the other hand, dent scratches include scratches, pinholes, and dents.
(3) Size of scratches: The size of scratches depends on the type of scratches. Blistering scratches are not so noticeable even if they are large, but dent scratches, especially white gouged scratches, are not so big. It stands out very well.
④Position of the scratch・・・Even if the scratch is small, the evaluation will change greatly depending on the position. For example, if there is a scratch on the "heaven" part of a craft beads, even if the scratch is small, the evaluation will be greatly reduced. On the other hand, scratches near the mouth of the hole are almost invisible in crafted products, so even large scratches will be evaluated loosely. Similarly, in the case of
, scratches on the conspicuous part that touches the skin, called the belly, are checked more strictly than scratches near the hole through which the thread passes.
Based on these evaluation points for scratches, Akoya pearls are classified into no scratches, small scratches, medium scratches, and large scratches. I do scratches together. Shirocho pearls are generally evaluated for scratches in the same way as Akoya pearls. No scratches), medium scratches, and large scratches. In the case of Kurocho
pearls, it seems that they do not take out only the scratch element and evaluate it together with the shape.
"Teri" refers to the quality of light reflected by pearls. Beads with good terry reflect light very brightly and sharply, but beads with poor terry reflect light weakly and are diffuse and dull. It will be. These differences in luster are determined by the properties of the nacre, such as its thickness, uniformity, and light transmittance. First of all, regarding the thickness of the mother-of-pearl, even thin ones have a good luster. However, if the mother-of-pearl is thin, the luster lacks the depth that is characteristic of pearls. Next, regarding the uniformity and light transmittance of the nacreous layer, even if the nacreous layer is thick, it will not produce a good result if the irregular crystals overlap. The aragonite that makes up the mother-of-pearl is large, thin, and clean plate-like crystals, and when many layers of these crystals are regularly stacked, the effects of light reflection, refraction, and interference give rise to the peculiar luster and color of pearls. It is. If the aragonite crystals are small, even if the fine crystals are stacked regularly and the nacre layer is thick enough, good luster and color cannot be produced. The uniformity of these crystals is closely related to aquaculture management. In the case of Japanese Akoya pearls, when the water temperature drops in winter, clean, thin and large crystals form, which improves the luster and color of the pearls, so farmers call this "cosmetic winding". The reason why Akoya pearls are hamaage in winter is that the nacreous layer of this season has the most beautiful luster and color. If the water temperature continues to be high during the hot summer months, or if the oysters weaken due to lack of food, the crystals formed will dissolve and the uniformity of the mother-of-pearl will be impaired, resulting in poorly lustrous pearls.
Evaluating Teri is probably the most difficult quality. This is because the evaluation of teri must consider not only the luster of the pearl, but also its curl and color. The original luster of pearls is a deep and soft luster, but recently, the surface luster that shines "shiny, shiny" is emphasized, so even thinly wound pearls have to be thoroughly surface-polished in order to make the luster look good. is often It is often thought that the quality of pearls is determined by the luster, but this is because the pearls are durable, that is, they have sufficient windings.
It's all about that. We must not forget that the conditions required for the quality of pearls are "beauty" and "durability" at the same time.
There is no standardized evaluation of luster, but it can be roughly divided into 3 to 5 grades, from very glossy to almost nonexistent. In the case of Akoya pearls and White butterfly pearls, there are 3 grades of teriari, medium teri, and terinashi, but in the case of Kurocho pearls, the range is quite wide, so it seems that there are many 5 grades.
Pearl colors are very complex. Even the same pearl can look slightly different depending on various factors such as viewing location, time of day, season, weather, type of light (direct or indirect light, color rendering properties of lamps, etc.). There are three major factors that determine the color of pearls.
The first factor is the action of light. As mentioned in "Teri", the effects of light reflection, refraction, and interference greatly affect the color of pearls. Interference of light in particular creates iridescence peculiar to pearls. This is because the same phenomenon that occurs in pearls occurs when an oil droplet is dropped into a puddle, or the beautiful iridescence of a soap bubble.When large, thin aragonite crystals are stacked uniformly and regularly, the interference color becomes stronger and the depth of the color increases
The second factor is the pigment contained in the conchiolin that makes up the pearl. The main pigments are yellow pigments in Akoya pearls and white pearls, black pigments in black pearls, purple and red pigments in freshwater pearls, and red pigments in conch pearls. There is almost no component analysis of these pigments, and there is only a report that the red color of conch pearls is a carotenoid pigment.
However, even if we do not know the structure of the pigments, we use the mechanism of pigment expression to control the color of pearls in actual cultivation sites. For example, with Akoya pearls, if pieces taken from oysters that do not have a yellow pigment are used, the appearance of yellow pearls will decrease. doing. Conversely, with white pearls, gold-lipped white pearls with yellow pigments are used to create golden pearls. In addition, it is known that black pearls and freshwater pearls can have different colors depending on the color of the pearl layer of the shell used for piece oysters and the part from which the piece is cut. It has been. In the case of freshwater pearls, it has also been found that inserting a piece of a different species of shellfish, such as a mussel or a mussel into a mussel, produces pearls of various colors. Since it is very difficult to change the color of pearls formed during culturing by physical and chemical means without impairing the quality of the
pearls, the color can be controlled during the culturing stage. It is desirable.
The third factor is organic matter. It is said that the cause of the formation of this organic substance is mainly bleeding during nucleation and metabolic abnormalities of the mother shellfish. Bleeding during nucleus implantation or abnormal metabolites left between the nucleus and the mother-of-pearl as dark brown organic matter will cause the pearl to appear blue when viewed through the mother-of-pearl. In other words, blue Akoya pearls and white pearls are not due to the blue pigment, but the dark brown stains that make the pearls look blue. Note
as this stain will fade due to drying and air oxidation after hamaage. Many of the Akoya pearls that are often marketed as “natural blue” are blue pearls that have undergone some kind of anti-fading treatment.
I have already mentioned the three factors that affect the color of pearls, but these factors are not isolated, but are intricately intertwined to produce the deep green pink of Akoya pearls, the vivid golden color of white pearls, and the peacock color of white pearls. Each mollusk produces its own unique color, including the iconic Black Butterfly pearls, deep oranges and purples, and metallic freshwater pearls. Pearls with good color and luster generally have tight windings, contain a large amount of pigment, and are good quality pearls with lightfastness
. In addition to these three factors, the color of pearls is also due to processing, as mentioned above. Please refer to the schematic diagram of the factors that affect the color of pearls.
Because the color of pearls varies considerably depending on the type of mollusk, each mollusk is evaluated separately.Akoya pearls are classified into pink, white, green, rosé, cream, yellow, golden, blue, etc. Depending on the trader, they are further subdivided into green pink, cream pink, etc. ), silver (including silver pink and silver blue), gold, fancy, cream, and others. In addition, black pearls have a wider variety of colors than other pearls, so if you subdivide them, they are endless, but they can be roughly divided into gray, black, green, red, peacock green, white, and blue. . Freshwater pearls come in three basic colors: white, orange, and purple, and these intricate mixes are expressed in various ways within the industry, such as wine, lavender, cognac, and apricot.
Determining the colors of pearls is not that difficult, but it is very difficult to answer the question, "Which color is best?" As mentioned above, the color of pearls is closely related to the winding and luster, so it is not possible to ignore these factors and evaluate by color alone. is needed.
Size was once an effective way to determine the type of cultured pearl mollusk. For example, the size range of Akoya pearls is 2 to 10 mm, and there are very few pearls larger than 10 mm. On the other hand, most white pearls and black pearls used to be larger than 10 mm, so they are easily distinguished from Akoya pearls by size. I was. Recently, however, the size of white and black pearls has become smaller, down to about 7 mm, making it difficult to distinguish them from Akoya pearls. Also, as freshwater pearls have improved in shape and color and become rounder, it has become difficult to distinguish them from other pearls by size.
Pearl size refers to its diameter in millimeters (mm). Round-shaped particles are usually sifted through a sieve, and the size that does not fall out is indicated in mm. Drop-shaped, oval, button-shaped pearls, black pearls, and freshwater pearls, which are difficult to sieve, are measured by their short and long diameters and marked as 8.5mm x 11.2mm. The size of Akoya pearls is indicated in millimeters or 1/2 millimeters, but for other pearls, the size is indicated to two decimal places, such as 9.25mm, and in some cases, 10.8mm. It seems to be a single digit, and the notation
is different depending on the vendor.