Stone Borers

Stone Borers

 

marine animals and plants that destroy rocks, coral, and mollusk shells. Stone borers include some species of marine algae, sponges, bristle worms, barnacles and iso-pod crustaceans, bivalves and gastropods, and sea urchins. Most stone borers make passages in rock mechanically (crustaceans, bivalves of the genus Pholas, sea urchins), but some destroy rock by chemical means, secreting an acid substance (blue-green algae, worms, and, of the bivalves, the “sea dates” of the genus Lithophagus). Stone borers use the passageways they have made as hiding places from enemies, as a place in which to keep wet during ebb tides, and as a refuge from breakers. Rocks that have been largely damaged by stone borers are eventually completely destroyed by the action of waves. In subtropical and tropical seas stone borers do much damage to concrete structures.

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In Egypt, this particular borer has been discovered at Hierakonpolis, a site associated with late predynastic and early dynastic stone vessel production (Quibell & Green 1902: plate LXII, 6) (FIGURE 1b); Mesopotamian figure-of-eight shaped stone borers were discovered by Woolley at Ur (Woolley 1955: 75, figure 15b) (FIGURE 1c).
Striations on Mesopotamian vessels, and the bottom surfaces of stone borers, are similar to striations seen on their Egyptian counterparts -- generally 0.
Stone borers, in particular the figure-of-eight shape, were mainly used to enlarge holes already made by a tubular drill.
The use of figure-of-eight shaped stone borers of different dimensions allowed gradually changing internal diameters to be ground, and the initial process of undercutting vessel shoulders.
Dry sand abrasive was employed, as previous experience with copper tubes and stone borers (Stocks 1988: 124--32) has determined that wet sand abrasive is not efficient.
It was excavated by two copper tubes, and stone borers (Stocks 1988: 192--212).
Boring the hole to match the bulbous exterior, by figure-of-eight stone borers, occupied another 10 hours.
It is apparent that ancient Mesopotamian and Egyptian stone vessel craftsmen must have adopted the twist/reverse twist manner of driving their tubular drills and stone borers.
The experiments demonstrate that the twist/reverse twist technique provided the only satisfactory method any ancient stone vessel craftsman could have employed for driving tubular drills and stone borers.
Two weights were fastened immediately under the inclined and tapered top part (see FIGURE 3a) to place a load upon a drill-tube or stone borer.
Another type of stone borer -- an inverted truncated cone with two slots cut opposite each other in the upper, horizontal surface -- was employed to shape a vessel's mouth (uncatalogued cone, Petrie Collection, University College, London).
In using a figure-of-eight stone borer, the craftsman must periodically change the position of his hands, in order to cut evenly around the whole circumference of a vessel.