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DIAMOND
The diamond cutting uses for the better the light and propagation laws (reflection, refraction, dispersion), by this way it determines the proportion to give flash, brillance and sparkling.
The size is evaluated by cara, ofcourse, te dream consists in having the biggest and flawless cara. The size is the most important criterion in the evaluation of a diamond. A cara weighs 0,20 g.
Follow the advice to preserve the splendour of your diamonds:
Detergent bath: pour liquid soap into a little bowl with warm water. Clean the jewels with the help of a brush for brow in the soapy water,then put them in a little strainer before rinsing them through warm water from the tap. Dry delicately with a cloth without ribbons.
Cold water bath: prepare in a cup a solution with half of cold water and half ammonia. Let the jewels to soak 30 minutes before taking them out and cleaning them delicately around the setting with a brush for brow. Plung them into the solution for the last time then mop with a tissue.
Ultra sonic cleanner: there are several machines of that kind in the market able to clean in few minutes the jewels which can be plunged into liquid. Each model is a bit diferent, so you should read the directions of use before using the machine.
PEARLS
Pearls form inside bivalve sea mollusc such as oisters. They result from the reaction of such animals to foreign bodies which entered between the shell and the mantle of the oister, and sometimes even inside such mantle. The foreign bodies can enter by a natural or atificial way. In the case of cultured pearls, white or colored ones, the insertion is made by the men. This complicate operation consists in introducing into the conective tissue of the mantle of an oister taken in the open sea, little nacreous and polished spheres, wrapped with a piece of epithelium coming from another pearl oister mantle. In any case, the insertion if an element in an oister provoks a reaction of natural defense, by which the foreign body is covered little by little with nacre "mother-of-pearl" and becomes at the end a pearl. The pearls can have diferent colors : white, black, grey or pink, yellow or even blue-grey glints. The most common and prized pearls are the round ones, extracted from Akoya oisters. Australian and Tahitian pearls are higher and darker with a grey steel color or black with green lights.
METALS
GOLD:
Color:
Gold is naturally yellow but we can obtain 3 main shades:
- pink
- yellow
- White (also named grey)
The nuances depend on the metals of used Alloy (silver, brass, nickel). Gold is extremely malleable and in order to transfer it better, we must alloy it with other metals. In France, 750 thousandh, So 75% pur gold, is authorized to be considered as gold.
According to the law, any piece of work having gold or platinium must be hallmarked as they get a weight higher than 3 grammes. The 585 thousandth and 375 thousandth are defined as gold alloy.
Point of fusion of pure gold : 1064°C.
Main solvents: mercury and special water ( hydrochloric acid + nitric acid)
PLATED GOLD:
It is a golden layer put on a (no precious) metal by diferent treatments of surface.
SILVER:
Silver is a precious metal with a natural white grey color. In France there are two titles: the 925 thousandth and the 800 thousandth.
According to the law, any piece of work holding silver must be hallmarked as they get a weight higher than 30 grammes.
VERMEIL:
It is superposing a golden layer on silver.
SAPPHIRE
The sapphire is one of the most resistant stone on the market.
With a hardness of 9 on the Mohs scale, the sapphire is harder than any stones, apart from the diamond. It is the ideal stone for an engagement ring ; this is the stone chosen by Prince Charles for Princess Diana's ring.
the blue color is dued to the iron oxide and titanium. The variant colors of sapphire are from white to pink, with also orange, gold, yellow, green, crimson and purple. The widely spread cutting is oval beacause it corresponds for the better to the rough form of the stone.
RUBY
The stone part of the family of the corundum or more precisely of the oxidized aluminium cristalline, is one of the most resistant mineral.
The corundum has the hardness of 9 on the Mohs scale.
The ruby forms especially (but not exclusively) into marble, metamorphic rock composed with calcium carbonate, which has been developed with high temperatures and under extremely high pressures.
The ruby is not extracted directly from the rock : indeed, we find it in stony alluvial deposits dued to the erosion of the mountains.
EMERALD
Hardness from 7.5 to 8.0 on Mohs scale.
The color of the Emerald goes from blue/ green to green / yellow, counting all range of the sweet and deep green. The chromium and iron give the green / yellow color, and the chromium and vanadium give the blue green color. The emerald is the only stone of Beryls which is classified among the family of the precious stone.
AQUAMARINE
Hardness from 7 1/2 to 8 on Mohs scale.
The caracteristics the most appreciated of the aquamarine, stone among the family of Beryls, are the clearness and the size of the crystals. A piece of 110kg, perfectly transparent, has been discorvered in 1910 The cutting of the table and of the steps are the most apropriate, because they emphasize the aquamarine's transparency. The round, oval, pear or faceted stones are also used and they preserve in the same way the splendour of the stones. For the aquamarines which are not transparent, the best cutting is the cabochon The main reserves are located in Brasil, the Ural region, Namibia, Zimbabwe and China. In Madagascar we find stones with a magnific blue-grey color.
TOPAZ
Hardness 8 Mohs scale
The topaz is a silicate of aluminium. The stone is made of aluminium, silicium and oxygen, but also fluorine and an ion of oxhydrygen (group formed by an atom of oxygen and an atom of hydrogen).
The topaz is in general cut in oval, classic shape which allows to underline the diferent shade and lighting effects. But some jewellers prefer the rectangular cutting (with table and degrees). The cabochon cutting ( round dome on a straight base) is scacier; it is often for gems which are not transparent or with inclusions. The dark yellow topaz is a very appreciated gem: it strongly seems to citrine, a variety of quartz.
The intense blue topaz is often used to imitate aquamarine, stone with higher value.
A wide range of museums all over the world are proud to have remarkable topaz. The biggest known topaz (3270 caras) is at th Smithsonian Institution of Washington. The British Museum of London has a topaz of 614 caras.
AMETHYST
Hardness 7 on Mohs scale.
The amethyst is the most prized stone of the quartz's group. It is attribuated supernatural powers : it is a talisman which brings luck and strength, protects from spells, from the nostalgia for one's mother country, and even from drunkness, as can mention the greek etymology of its name : "amathustein" ("to not be drunk"). For ages, the stone has been reckonized for two main virtus: it protects the crop against insects and preserves the beauty of the women. Moreover, in the Christian history, the amethyst, symbol of pity, was the ony stone carried by the most powerful men of the Church. In the heraldry, the science of blazons, the amethyst embodies the sense of decency. The beauty of the amethyst is dued to the origins of the stone, which is often located in the cavities of the rocks. There are many deposists of deep purple amethysts in Brazil, Uruguay and in the Ural region, while Mexico is famous for the purple-red amethyst. We can also find other deposists in Sri Lanka, South Africa and Europe (France, Germany and Italy).
CITRINE
Hardness 7 on Mohs scale.
Sometimes mistaken for topaz, the name citrine is dued to lemon, « citrus » in latin, because of its yellow color. It is part of the quartz group. This stone is located in several deposits in Brazil, India, Madagascar, Uruguay, Mexico and Sri Lanka. Citrine is as considered as the amethyst or the rock crystal, even if the two latter have always been more used. The citrine is adapted for all faceted cutting, and this stone has scarcely inclusions.
TOURMALINE
Hardness: from 7 to 7.5 on Mohs scale.
The stones were very popular under the Roman Empire particularly as adornment stones to embellish objects and jewels, then they were used for the sacred art (cf. Duomo di Monza Treasure). They were taken into Europe by Dutch sailors in about 1700. The tourmaline can take numerous colors (among them pink, red, green, yellow, violet and blue) according to the following chemical elements: chromium, iron, titanium, brass, manganese and vanadium. The tourmaline deposits are located all around the world : Afghanistan, Brazil, India, Kenya, Madagascar, Mozambique, Namibia, Nepal, Nigeria, Sri Lanka, Tanzania, Zambia and Zimbabwe.
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