History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c17.s2.t2: Steatite Beads
History of Technology in India, Vol. I: From Antiquity to c. 1200 A.D. v1.c17.s2.t2
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Steatite Beads
v1.c17.s2.t2.1
Small blocks of steatite in light yellow, dark-grey and black were not uncommon in various parts of Mound II. Many of them bear the marks of the saw which had cut them up into shapes suitable for both beads and seals. Pieces that could not be used for any other purpose were ground into powder and then compressed into blocks, from which beads and even occasionally seals were made. This made-up steatite is always white in colour and was probably calcined before compression. It is often very difficult to detect the difference, especially as objects composed of it are more often than not coated with a glaze.
v1.c17.s2.t2.2
Although Hoarce Beck was not disposed to agree that reformed steatite was used by the people of the Harappa culture, F.A. Bannister of the Mineral Department of British Museum reported that steatite paste would become indistinguishable from the natural material after being subjected to a very high temperature. In ancient India, the steatite beads were sometimes heated to a temperature exceeding 1200°C, and it has been proved that (the heap of ) minute beads were treated to this degree of heat. These must have been composed of a paste which could be forced thorough fine tubular instruments.
v1.c17.s2.t2.3
Among all the beads found from Chanhu-daro, the pile of minute steatite beads was an exceptional find. The manner in which these beads lay in lines on the pile proved that these were originally strung together. F.A. Bannister and G.F. Claringbull of the Mineral Department of the British Museum who examined some of these beads, reported that the beads are small hollow cylinders which vary in external diameter 1/2 (.019 inch) to 1 mm and in length from 1/2 to 1 1/2 mm. When freed from loosely adherent soil, they are pure white and very hard. Nearly every bead is furrowed along its length spirally, always in a clock- wise direction. It is not uncommon to find two beads joined together with the spiral furrowing running continuously and in perfect alignment from one to the other. The physical and chemical data are conclusive about the material from which these beads were made. Their specific gravity is 2.85 and the refractive index of crushed fragments is 1.60. The beads can be fused only in the electric arc, and then yield glassy spheres with a lower specific gravity 2.72. Except magnesium and silicon no other element could be detected with the quartz spectrograph. X-ray powder photographs show that the beads are steatite that has been completely dehydrated and heated to a temperature exceeding 1200°C.
v1.c17.s2.t2.4
Recently, Hegde et al (1982) have examined the Harappan microbeads made of steatite and obtained from Zekda, located in Banaskantha district in the northern part of the Gujarat State. The raw material was aluminium-containing talcose steatite available in Ambaji near Zekda. The X-ray diffraction patterns in the finished beads revealed the presence of silica in the form of cristobalite and anhydrous magnesium silicate in the form of enstatite. When talc is heated around 900°C it loses its water of crystallisation, forms cristobalite and enstatite, and improves its hardness from one to seven on the Moh scale.
v1.c17.s2.t2.5
The Harappans used steatite, a soft stone for making seals and beads and then hardened the same. A paste of finely ground talcose steatite was squeezed through one millimeter diameter perforations having 0.5 mm diameter copper of bronze wires in the centre of the perforations to produce hollow tubes which were cut into small bits and then hardened by firing at 900°C. According to Hedge et al, this was the method of production of steatite beads.
v1.c17.s2.t2.6
The majority of the beads found at Chanhu-daro were unfinished, broken in boring which proves that these were actually made at Chanhu-daro. This inference has been corroborated by the discovery of the bead factory with furnace here. To the north-west corner of the main street of the Mound II was a remarkable building with several furnaces; this evidently housed the bead factory amongst other fabrication facilities.