Materials The natural properties of gold, such as its resistance to tarnish, its lambent yellow colour, its weight and plasticity, distinguished it from the outset as a medium for accumulating wealth or creating luxury objects such as jewellery. Gold, one of the first metals used by man, is found in veins, mainly between pyritic minerals such as quartz, from which it is also mined. As these minerals weather, particles of gold are released and washed away by rainwater into the rivers. The collection. and separation (panning) of alluvial gold constitutes probably the most ancient process for obtaining this precious metal. In antiquity there were gold deposits around the Mediterranean in Egypt, Spain, the Caucasus and elsewhere. It would be remiss not to mention some of the gold mines in Greece, such as those of Siphnos, Thasos or Mount Pangaion.

Fig. 3 Gold belt inlaid with rock crystal, 3rd century BC. (Athens, National Archaeological Museum, ST.353).

Another noble metal is silver. The whitest metal, its surface can be polished to a high degree, while in pure state it is second only to gold in malleability and ductility. These qualities were decisive for the use of silver in jewellery-making. Native silver is rarely found. The principal source of the metal in antiquity was the ore galena (lead sulphide PbS) of which there were rich lodes at Laurion. Another source of silver was its natural alloy with gold, electrum. During antiquity electrum was either used native or broken down into its two valuable components by the process of cupellation. This same method was employed for extracting silver from galena. Cupellation is based on the different behaviour of metal oxides on heating: In the case of galena the impurities are first removed and the metals converted into their oxides. These are then placed in crucibles (cupels). On heating the lead oxide is absorbed by the porous walls of the crucible, while the silver oxide decomposes, leaving the pure silver at the bottom.

Fig. 4 Gold earring, 5th century BC. (Athens, National Archaeological Museum, XP.928).

Copper is considered to have been the first metal used by man. It has great thermal conductivity, is easily modelled, anneals and solders well, while displaying great ductility. It occurs native in small : quantities. The first ores from which copper was obtained were its oxides (cuprite), followed by the sulphates (chalcanthite), carbonates (azurite, malachite), sulphides (chalcocite) and others. One of the most important sources of copper in antiquity was Cyprus, for which reason the Latin word for copper, cuprum, derives from its name.

Man discovered very early on that it is preferable to use metals in alloys because these have better properties. Thus while gold is soft, its alloys with silver or copper are much harder. Silver was mainly used in alloys with copper. The first alloys of copper were with arsenic or antimony, but from the time tin was discovered this replaced them. From Roman times zinc began to be used too. Another component that frequently occurs in copper alloys is lead, which imparts plasticity.

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