Minerals and Metals in Ancient India v1.c19.s5.t5: Glass Pieces
Minerals and Metals in Ancient India v1.c19.s5.t5
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Glass Pieces
v1.c19.s5.t5.1
A small piece of glass was examined and analysed. It was dark green in colour. It is obvious that it formed part of a bottle or some other receptacle. The results of chemical analysis give 56.96 per cent SiO₂, 4.46 per cent Fe₂O₃, 3.62 per cent Al₂O₃, 1.09 per cent Cr₂O₃, 1.06 per cent PbO, 0.89 per cent SnO₂, 7.00 per cent CaO, 3.75 per cent MgO, 17.55 per cent Na₂O and 4.09 per cent K₂O.
v1.c19.s5.t5.2
The amount of alkalies in the glass piece is rather high. It is a soda-lime soft glass. The colour is due to the presence of iron and chromium. (Gaur: 1983, 490) This is one of the earliest evidences of glass being made in ancient India.
v1.c19.s5.t5.3
Hegde (1987) has suggested that glass in India was an innovation of the PGW period, and *sajjī maṭṭi*, also called *reh*, *khari*, was used for making the early variety of soft glass. *Sajjī maṭṭi* is an alkaline, natural efflorescence, profusely found in the Ganga Valley, chiefly in mid-eastern and eastern Uttar Pradesh and Bihar. During the summer months, it comes out as a superficial incrustation on the alluvial soil as a 2-3 cm thick layer of glistening, white, crystalline salt, shining brightly in sunlight. It assays 20-40 per cent soda, variable proportions of Na₂CO₃ and Na₂SO₄, 5-10 per cent lime and 50-70 per cent silica; its use with some raw material containing Fe and Cr in making the dark green soft glass, as mentioned in the previous paragraph, can be easily surmised. *Sajjī maṭṭi* was also used in providing the liquid glaze on the later day NBP wares.
v1.c19.s5.t5.4
Hegde (1987) examined thin sections of PGW and found ‘insignificantly small number’ of larger and heavier particles of feldspar, quartz or limestone, thus proving the thoroughness of labour that the ancient potters had put in to prepare well-elutriated fine clay before making PGW. Red ochre containing Fe₂O₃ must have been used as the painting medium to decorate PGW before baking in a reducing atmosphere (in a *gajapuṭa* type of sealed furnace in which carbonaceous matter burned in an insufficient supply of oxygen producing carbon monoxide) since the black paint on the PGW has been proven to be Fe₃O₄ or magnetite. It is noteworthy that in this PGW era, one further step of reduction of iron oxide led to the first ever production of iron metal in India.
v1.c19.s5.t5.5
Fe₂O₃ → Fe₃O₄ → Fe
v1.c19.s5.t5.6
Although not much gold and silver have been found from any PGW site, which shows that the Harappan type of affluence re-emerged only much later in the NBPW era, Atrañjikhera excavation has yielded an interesting soapstone fragment of a mould which could have been used to prepare gold jewellery.