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Property of a Lady GERARD A SUITE OF SAPPHIRE AND DIAMOND JEWELRY Comprising a necklace, designed...

Currency:USD Category:Everything Else / Other Start Price:NA Estimated At:50,000.00 - 80,000.00 USD
Property of a Lady GERARD A SUITE OF SAPPHIRE AND DIAMOND JEWELRY Comprising a necklace, designed...
Property of a Lady
GERARD
A SUITE OF SAPPHIRE AND DIAMOND JEWELRY
Comprising a necklace, designed as a supple and tapering band of overlapping swags set with brilliant-cut diamonds, suspending a fringe of five oval-shaped sapphires within brilliant and pear-shaped diamond surrounds, with pear-shaped diamond drop spacers; and a pair of earpendants en suite, mounted in 18K gold, French assay marks, necklace length 41.0 cm
Signed M. Gerard
ESTIMATE CHF 75,000 - 120,000
$ 50,000 - 80,000
PEARLS
PHILLIPS Pearls
The Swiss Gemmological Institute's Prof. Henry A. HSnni shares his knowledge of this organic gemstone
Pearls are among the most beautiful adornments OF jewellery. They are considered organic gemstones. While other gemstones are usually minerals, deriving of inorganic nature, pearls are created by animals, either accidentally or by the voluntary intervention of man. Speaking of pearls we have to respect some simple nomenclature rules. These rules apply terms which define clearly the nature of pearls. The three major terms are: natural pearls, cultured pearls and imitations. The latter are produced industrially of any material which gives the superficial appearance of pearls. They consist of a round bead and a lacquer with a pearly lustre.
Natural pearls are formed accidentally by wild shells without any intervention of man. Natural pearls are extremely rare compared to the cultured or imitated pearls. Natural pearls may grow in seawater oysters or freshwater shells. Approx. 15 different species of seawater oysters and approx. 20 species of freshwater shells were found to produce nacreous concretions i.e. pearls. The pearls consist of mainly calcium carbonate CaCO3 and a small amount of organic material (conchyoline, framework proteine). The central part of natural pearls consists often of columnar calcite which is overlain by a nacrous layer. Its pearly sheen or orient is due to light scattering and interference on a parallel array of microscopic tablets of aragonite CACO3. The aragonite tablets are disposed like tiles in concentric layers and have a thickness of about 500 nm. A daily deposition rate of 15 to 20 tablets seems a reasonable figure for most of the pearl producing shells. The nacreous aragonite is also called mother of pearl and in a round pearl it is deposited in a concentric array. This substance is secreted by a thin skin or mantle epithelium that lines the interior of the shell. This epithelium has in fact also produced the whole nacreous part of the shell. Its speciality and only capability is the secretion of substances that reinforce the shell. The outer mantle epithelium is also key to the production of cultured pearls. Damaging the mantle epithelium at the outer rim of the shell where it is thin and fragile, may lead to a natural pearl. Crabs, parasites and other enemies which attack the shell may wound the epithelium, and disconnect some cells from the tissue. Embedded in the mantel, these cells may survive and form a small pocket in which they secrete their product: calcium carbonate. The pocket is called pearl sack, and grows with time, as does the shell itself. After a couple of years, a pearl may have formed and the shell be found by a pearl fisher.
Among the pearl producing shells there are species with different colours of nacre. We encounter thus white, creme, golden, rose, grey and black pearls. A natural pearl of a certain size, e.g. 100 ct must be considered historically important, as the Hope Pearl (454 ct). The shape of a pearl is not always round and may be described as button, drop or baroque. Natural pearls may sometimes survive centuries and still keep a good appearance. When a pearl is accidentally attached to the shell it may be cut away and the back be worked in order to get a usable shape. Such pearls are then called blister pearls. Very small pearls such as 2mm in diameter are called seed pearls. The weight of pearls is often given in grains or carats, 4 grains is 1 ct (200 mg).
Except for nacreous pearls produced by shells (bivalves), we rarely may see porcellaneous pearls produced by seawater gastoropods (snails) which lack the pearly sheen. The most well known porcellaneous pearls are the Caribbean conch pearls or pink pearls. They often show a flame structure on the surface. Another rare kind of porcellaneous pearls are the rare orange Melo pearls which reach important sizes of up to 30 mm. They are occasionally found in Halong bay (Vietnam). Porcellaneous pearls are also composed of calcium carbonate, but instead of aragonite tablets they consist of bunches of aragonite fibres.
Natural pearls are quite rare today and highly priced when in good shape, colour and with appealing lustre and orient. A major difficulty in assembling a strand for a necklace is to find enough matching pearls. They have to match in size, shape, colour, surface and lustre. A huge number is necessary to get a satisfying match. Usually the pearls are graduated in a strand from smaller size to the larger central pearls. Necklaces with pearls of equal size are called chokers. Today natural pearls are still fished and may come from the Persian Gulf, the Gulf of Mannar, or Central America. They are extremely rare compared to the number of cultured pearls produced in numerous farms worldwide.
The identification of pearls is safely done by X-ray testing methods, using mainly the direct radiography method. An x-ray shadow picture is produced on a fine grained film, and the internal structures are then studied with magnification. The SSEF Swiss Gemmological Institute has produced test reports on diamonds, colour stones and pearls for over 25 years. The main task in pearl testing is to identify the pearls as natural or cultured. Scientific methods and a highly educated staff guarantee safe results and ensure the trade with valuable pearls. Research on pearls and nacre was necessary to understand the phenomena and characteristics encountered. Conclusions of our research have been published in scientific and gemmological journals. A further field of testing coloured pearls is the authenticity of colour, i.e. identification of a possible treatment. Only by using sophisticated instruments, can pearl testing be performed to the necessary reliability, and the analytical equipment involves UV-VIS-NIR spectrometry, Raman spectrometry, and X-ray fluorescence spectrometry.
We consider it a privilege to work in an important gemmological laboratory and have access to rare and exceptional jewellery pieces. It is this situation which provides the gemmologists with unusual experience. Besides gemmological testing of pearls the author has been performing research in material science by investigating pearls and shell material. Visiting pearl farms and diving to the wild oysters in various oceans also contributes to the detailed picture that enables us to understand pearls in all their variations.
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