62. The natural \inds of earth, which are useful as well as superior in quality, are three or four in number, the Melian, the Kimolian, the Samian, and a fourth in addition to these, the Tymphaic or gypsos.
Melian earth, which was found in Melos, an island in the Cyclades, is mentioned by several other ancient writers. Most of them say or imply that it was white, but Dioscorides491 states that it was ash-colored like the Eretrian earth. This suggests that it probably occurred both in a white and a greyish form. For use as a paint pigment it is probable that only the white form was suitable. Later in this section Theophrastus compares it with Samian earth and gives the impression that it felt rough when it was touched. Dioscorides specifically says that it was rough, and that when it was rubbed between the fingers it made a sound, just as pumice does when it is rubbed. Various conjectures have been made about its identity. Hill492 described it as a fine white marl, though he gave no reason for this. Lenz493 thought that Theophrastus was describing a clay, or a chalky clay, and various writers have identified Melian earth as a white clay, though they do not seem to have had any actual knowledge of the kinds of earthy minerals that occur on the island of Melos. However, Stephanides494 did know that deposits of kaolin occur on Melos, and he also identified Melian earth as a pure white clay or kaolin. But there is an objection to this identification, since tiie statements of both Theophrastus and Dioscorides plainly show that this earth was not unctuous like clay, but harsh or rough to the touch. Though some impure clays feel rough because of the presence of sand, it seems more likely that Melian earth was not a clay at all but some other substance such as a siliceous earth. What makes this very probable is the actual occurrence of a white siliceous earth on Melos, where several large deposits have recently been discovered and exploited. This is a brilliant white earth that occurs in chalklike masses. It consists of nearly pure silica in a cryptocrystalline form. Though it is soft and extremely fine after the
491 V, 179 (Wellmann ed., V, 159). i92Theopkrastus's History of Stones, p. 142.
493 Mineralogie der alien Griechen ur.i Romer, p. 27.
494 The Mineralogy of Theophrastus, p. 93.
