Jewellery (also spelled jewelry, see spelling differences) is a personal ornament, such as a necklace, ring, or bracelet, made from jewels, precious metals or other substance.
The word jewellery is derived from the word jewel, which was anglicised from the Old French "jouel" in around the 13th century.[citation needed] Further tracing leads back to the Latin word "jocale", meaning plaything. Jewellery is one of the oldest forms of body adornment; recently found 100,000 year-old Nassarius shells that wereAlthough in earlier times jewellery was created for more practical uses, such as wealth storage and pinning clothes together, in recent times it has been used almost exclusively for decoration. The first pieces of jewellery were made from natural materials, such as bone, animal teeth, shell, wood, and carved stone. Jewellery was often made for people of high importance to show their status and, in many cases, they were buried with it.
Jewellery is made out of almost every material known and has been made to adorn nearly every body part, from hairpins to toe rings and many more types of jewellery. While high-quality and artistic pieces are made with gemstones and precious metals, less-costly costume jewellery is made from less-valuable materials and is mass-produced. New variations include wire sculpture (wrap) jewellery, using anything from base metal wire with rock tumbled stone to precious metals and precious gemstones.
Agate is a term applied not to a distinct mineral species, but to an aggregate of various forms of silica, chiefly chalcedony.
According to Theophrastus, the agate (achates) was named from the river Achates, now the Drillo, in Sicily, where the stone was first found.
Most agates occur as nodules in volcanic rocks or ancient lavas where they represent cavities originally produced by the disengagement of volatiles in the molten mass which were then filled, wholly or partially, by siliceous matter deposited in regular layers upon the walls. Such agates, when cut transversely, exhibit a succession of parallel lines, often of extreme tenuity, giving a banded appearance to the section. Such stones are known as banded agate, riband agate and striped agate.
In the formation of an ordinary agate, it is probable that waters containing silica in solution -- derived, perhaps, from the decomposition of some of the silicates in the lava itself -- percolated through the rock and deposited a siliceous coating on the interior of the vapour-vesicles. Variations in the character of the solution or in the conditions of deposit may cause corresponding variation in the successive layers, so that bands of chalcedony often alternate with layers of crystalline quartz. Several vapour-vesicles may unite while the rock is viscous, and thus form a large cavity which may become the home of an agate of exceptional size; thus a Brazilian geode lined with amethyst and weighing 35 tons was exhibited at the Dusseldorf Exhibition of 1902.
The first deposit on the wall of a cavity, forming the "skin" of the agate, is generally a dark greenish mineral substance, like celadonite, delessite or "green earth," which are rich in iron probably derived from the decomposition of the augite in the enclosing volcanic rock. This green silicate may give rise by alteration to a brown iron oxide (limonite), producing a rusty appearance on the outside of the agate-nodule. The outer surface of an agate, freed from its matrix, is often pitted and rough, apparently in consequence of the removal of the original coating. The first layer spread over the wall of the cavity has been called the "priming," and upon this base zeolitic minerals may be deposited.
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