| Carburization A process in which the carbon content of a steel
is increased bv diffusion of carbon into the alloy. Cassiterite Tin oxide (SnO2). Cast iron An iron-carbon alloy cooled from a completely liquid state with a carbon content above 2 per cent, and with a minimum melting temperature of 1 143 °C at the 4-3 per cent carbon level. Casting The process of shaping an artefact by pouring molten metal into a mould. Charcoal Incompletely combusted wood providing a highly porous carbon-rich fuel. Crucible A refractory ceramic bowl in which glass or metal can be melted. Crucible furnace A smelting furnace incorporating a ceramic bowl in which the molten product is caught or retained. Decarburization The process of carbon loss by diffusion of dissolved carbon to the surface of heated steel. Drum bellows A synonym for bowl bellows, usually implying that the bowl is made of wood rather than of ceramic. Equiaxed grains Grains of more or less equal size and equidimensional shape. Fayalite Iron silicate (2FeO.SiO2). Ferrite The alpha form of iron containing up to 0-02 per cent dissolved carbon at 727 c. Flux An additive, often lime, employed to lower the melting temperature of the slag minerals and to promote smelting at lower temperatures than would be possible otherwise. Forced draught The active provision of air to a furnace by means of bellows. Forge A hearth, often with air provided by bellows, used for reheating metal during hot-working to fashion it into the desired shape. Forging The process of working a piece of metal while hot. Furnace An oven or containment in which a charge of ore and fuel can be heated sufficiently to allow smelting to take place. Galena Lead sulphide (PbS). Gangue The non-metallic, usually siliceous, component of an ore. Gossan The leached and oxidized weathered cap frequently present on the exposed surface of metal-rich geological occurrences. Haematite Iron oxide (Fe203). Heat treatment A variety of processes in which the physical properties of a piece of metal may be altered by controlled heating and cooling. Ilmenite Iron titanium oxide (FeO.TiO2). Lamp black Finely comminuted carbon deposited as soot. Laterite A leached soil, typical of tropical weathering, in which residual iron |
| oxide and silica are the major components. Lime Informally denotes calcium oxide (CaO) or calcium carbonate (CaC03), usually derived from shells or the surface rock calcrete, and used as a flux. Magnetite Iron oxide (Fe304). Malachite Hydrated copper carbonate (Cu2(0H)2CO3.Cu(OH)2). Natural draught The passive provision of air to a fumace by exploiting the chimney effect of hot gasses rising up the furnace to draw in air through numerous tuyeres at the bottom. Non slag-tapping furnace A furnace in which the molten slag collects near the bottom of the furnace and is retained until the end of the smelt. Nucleation The initiation of crystallization at discrete sites in a molten mass. Ochre Hydrated iron oxides used as pigments. Old wood problem Radiocarbon dating dates the event of the tree la! laying down the particular wood material dated. The use of a large tree laying down relatively old wood, or the use of old dead wood for fuel can result in an error of hundreds (and possibly even thousands) of years to radiocarbon dates run on charcoal assumed to be Contemporaneous with the event Or structure being dated. Oxidation 'I'he chemical combination of oxygen with an element or compound to form an oxide. Oxidizing atmosphere A gas atmosphere which promotes oxidation by the predominance of carbon dioxide over carbon monoxide. Partial reduction The incomplete reduction of an ore, resulting in some metal and some roasted or fused ore, or the presence of unreacted gangue materials in the smelting product. Pisolitic structure A texture consisting of small (c. I to 5 mm diameter) spheres, often comprising concentric shells of mixtures of iron oxides and silica, typical of laterites. Pot bellows A synonym for bowl bellows. Precision In radiocarbon dating, a measure of the reproducibility of a date determination. It is expressed as a plus/minus value after the mean date and is the standard deviation associated with the determination. Precision is distinct from accuracy. Pseudomorph An object displaying an inherited form indicative of the replacement of the original material by a secondary material. Pyrolusite Manganese dioxide (MnO2). Quartz Silica or silicon dioxide (SiO2), the predominant constituent of most sands. Quenching A heat treatment involving plunging a hot metal object into a relatively cold liquid to produce a controlled microstructure and thereby alter the physical properties. In the case of carbon steels this can harden and embrittle the metal very significantly. Reducing atmosphere A gas atmosphere which promotes reduction by the presence of significant quantities of carbon monoxide relative to carbon dioxide. Reduction The chemical removal of oxygen from a compound. |
| Roasting Relatively prolonged heating of ore nodules on open
fires to induce drying, cracking, partial break-down of sulphides, and to facilitate subsequent smelting . Shaft furnace A smelting oven incorporating a cylindrical or conical chimney, or shaft. Slag pool A puddle of molten slag, either trapped in the bottom of a non slagtapping furnace or drained to the outside from a slag-tapping furnace. Slag-tapping The practice of opening the base of a furnace during operation to drain the accumulated slag and allow the smelt to proceed without blocking the tuyere with slag. Slag The molten, or solidified, waste product of smelting, consisting of used components derived from the ore flux, fuel, and furnace lining. Slags can vary significantly in composition and microstructure and contain chemical and mineralogical information crucial to the reconstruction of furnace operating conditions. Smelting The process of chemically reducing an oxide ore to a range of products including workable metal by the application of heat in a furnace. Smithing The process of chemically reducing an oxide ore to a range of products including workable metal by the application of heat in a furnace. Solidus temperature The temperature at which a melt of any particular composition solidifies by crstallization Specularite Lustrous platy haematite, iron oxide (Fe2 03) Spherulitic structure A texture, commonly found in latterites, consisting of small spheres of iron oxides and silica often displaying a concentric internal structure. If the spherules are small the structure is described as pisolitic. Stack The conical or cylindrical shaft of a furnace, usually applied to a blast furnace. Standard deviation A statistical measure of the precision of a measurement, which in radiocarbon dating is quoted usually as + 1 sigma, implying that the true measurement value lies between the stated limits with a probability of 68 per cent. Steel An alloy of carbon in iron in which the carbon content lies between about 0.05 and 2-0 per cent. Sulphide ore In the context of ancient metallurgy, copper sulphide ores typically found at some depth below the oxidized and leached surface outcrops which were the initial target of early mining. Surface tension The cohesive force associated with the surface of any liquid. Tempering The heat treatment of a quenched metal at a moderate temperature of about 500 °C to allow partial recrystallization to take place in order to reduce the brittleness of the as-quenched material. Thermoluminescence A dating technique which relies on detecting the energy accumulated over time of radiation-induced defects in some crystalline materials which release this energy as light when heated. Tuyere An air pipe through which air is either pumped or drawn into a furnace. Valveless bellows Bellows without inlet valves, which rely on a loose fit between the bellows outlet and the tuyere to allow air to be sucked in through this gap. Wire drawing A technique for thinning a metal rod by drawing it through |
| successively finer perforations in a plate. Wustite An oxide of iron with the approximate formula of Fe(1-X) O. |