Steatite

A soft magnesian mineral, white to green massive rock composed mainly of talc. The softness of the stone made it very popular for the carving of artifacts: figurines, vessels, jewelry, decorative stone works, and stamp seals. Its resistance to high temperatures made it particularly suitable for mold-making for metal casting. In the Indus Civilization seals of this material were whitened by heating with lime, a process called 'glazing'.

Rock chiefly composed of the soft mineral talc. Also known as soapstone, steatite is easily carved to make artefacts such as bowls and figurines, and is also a convenient material for MOULD-making. steel. An alloy of iron with carbon. Steel appears in the archaeological record during the Iron Age and was usually produced by carburization of wrought iron (see iron and steel). In this process, the iron is heated in a hearth with charcoal to about 800°C. Carbon diffuses into the surface of the metal to make steel. As only the surface is affected, only thin strips of steel could be made by this method. Some Iron Age artefacts are made of piles of such steel strips, forged together. Steel for a cutting edge can be further hardened by quenching, where the red hot metal is plunged into cold water (or other liquid). This makes it very hard, but renders it undesirably brittle. The latter effect is counteracted by tempering — gentle heating (c200-300°C) in a hearth. The process of quenching and tempering was known from Roman times but early steels must have been rather too brittle for some uses. Many Viking swords combined the strength of wrought iron with the hardness of steel. They were made of many strips of the two metals, forged together, a technique known as pattern welding.