Commentary Page 159



	THEOPHRASTUS ON STONES

	from this one locality, it is evident that there were other sources of such an abundant material as slate, and even of alluvial slate. The wider distribution of the stone used by the ancients for touchstones is, in fact, specifically reported by Pliny.³³⁵ However, Theophrastus may be right in his statement about the source of supply in Greece during his lifetime, since slate, particularly the kind suitable for use as a touchstone, is by no means a common rock on the Greek mainland or on the islands of the Aegean. Black slate is a satisfactory material for touchstones, though modern touchstones are generally made from a velvety-black form of jasper, which is a much better material. 47. The top part, which has faced the sun, differs from the lower surface in its testing power and tests better than the other. This is because the upper surface is drier, for moisture prevents it from picking out the metal. This difference in the moisture on the upper and lower surfaces of the stone can only refer to the condition of the slate when it was picked up from the shores of the river or the dry parts of the river bed. It is easy to understand why the clean upper surfaces of such stones were superior to the lower surfaces, since the latter were not only damp but also probably impregnated with fine particles of clay which lubricated the surfaces and reduced the desired abrasive action of the stone. These remarks of Theophrastus probably do not refer to the use of touchstones in mints or in shops where objects of precious metal were made, but rather to their use for testing the quality of metal as it was being mined. Thus Theophrastus may be speaking of the touchstone used for testing the metal that was mined in or near one of the rivers of Mt. Tmolos. There is historical evidence that Mt. Tmolos was an important source of gold during the reigns of certain kings of Lydia, particularly Alyattes and his son Croesus (560-546 B.C.), though not later.³³⁶ It therefore seems likely that the information which Theophrastus is giving here may go back to these very mining operations. Moreover, it is not unlikely that the touchstone method of assaying may have come into use at the mines of Mt. ³³⁵ XXXIII, 126. See the notes on sec. 4 for a quotation of the Latin text. ³³<s Strabo, XIII, 4, 5.

	• 158 ·