GEMSTONES
Gemstones have been used for thousands of years in fashion jewelry making, to decorate, allure and attract the eye. Many stones were believed to possess magical or talismanic properties that would ward off evil. To this day, gemstones often form the focal point of a piece of jewelry, but can also be used to accent or highlight areas; gems are set, strung or mounted to give colour or sparkle.
Composition
The majority of gemstones are mineral in nature, fbrmed underground by pressure, temperature and other factors in igneous, sedimentary or metamorphic rock. The way in which mineral crystals form directly affects the properties of the crystal in terms of size, cleavage and fracture, and the type of optical effects that will be apparent when the stone is cut. Most gems are coloured by the presence of elements or minerals; for example, chromium and vanadium give emeralds their characteristic green colour.Gems with similar compositions are grouped into families – quartz is a large group of stones diat includes rock crystal, rose quartz, citrine and amethyst. Many gems are specific to a few geographic locations. A great deal of stones are treated to improve their colour and clarity, and this can be achieved through hearing, irradiation and laser drilling to remove inclusions; surface treatments include the application of waxes, oils or resins to improve the surface of a stone by filling cracks and flaws.Organic gems such as amber, pearls, jet and coral are considered precious materials and are produced from plant or animal sources in nature. Pearls are often cultivated, so natural pearls carry a high price. Amber is often reconstituted with synthetic resins, a practice that has been taking place since the mid-nineteenth century. Organic gems are generally much softer than mineral gems, so the range of applications they can be used for is more limited.
Applications
The visual and physical properties of stones vary greatly, and will influence the type of fashion jewelry they can be used for, and how they are secured in position. There are a number of different ways of using metal to ’set’ stones; in bezel and flush setting, metal is pushed down around the stone to secure it. This method is often used for setting cabochons, but can also be used for faceted stones. Fragile stones should be set with fine silver or gold, as these metals are softer in pure form. Prong or claw settings use shaped wire to form a frame that holds the stone proud of a piece, allowing light to enter around the stone. For more information on types of settings, A setting must be sympathetic to the stone in terms of its hardness, colour and cut; the type of setting may affect the intensity of the colour of the stone, and certain types of settings are more suitable for some cuts than others.Stones can also be used in their rough (uncut) form, and softer stones may be cut and carved.Beads can be strung on a wide variety of different media, including silk and nylon. The silk is knotted herween pearls and semiprecious beads to keep them from rubbing against one another, which would cause damage; it also means that if the string breaks then few, if any, beads will be lost.Stones may be bought with a specific design in mind, or can provide an inspirational starting point, but always consider the properties of the stone when deciding on the type of setting
