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Book V about lodestone, hematite, geodes, hematite, selenite, lapis secularum, asbestos, mica

Book V about lodestone, hematite, geodes, hematite, selenite, lapis secularum, asbestos, mica Page of 251 Book V about lodestone, hematite, geodes, hematite, selenite, lapis secularum, asbestos, mica Text size:minus plus Restore normal size   Mail page  Print this page
108
DE NATURA FOSSILIUΜ
Mysia. It is quarried at the town of Confluentia, so-called because it is at the confluence of the Moselle and Rhine rivers. It is found in Lower Germany near the famous town which takes its name from waters. Since pumice is as full of open channels as a sponge it is called lapis spongia, according to Vitruvius. It is called κίσσηρπ by the Greeks. This name, according to certain writers, comes from the name of the worm that eats grain and is called /as by the Greeks and gurgulius (weevil) by the Latins. It makes holes in the grain until it has the appearance of pumice. Theo-phrastus called the rock halcyonium because he thought it had congealed from sea foam but we have already discussed this mineral.
There are varieties of pumice. They are not all of one color since they may be black, gray or white. Some are so soft they can be ground to a sand in the hands, for example, that found on Nisida, according to Theophras-tus. Others are hard. All are porous and light because of the internal cavi­ties filled with air. Due to its porosity it will float on water as do other pumaceous stones no matter how large they may be. A pumaceous stone of this lightness is found on Thyrrae and another on the island of Nisida and these may be true pumice. Pumice which floats when whole will sink when crushed. Although all are light and porous the black varieties are denser and heavier while the white and gray varieties are lighter. Al­though it contains a large amount of air it will neither take fire nor burn because it lacks moisture. The force of fire destroys it. Because of its rough­ness pumice is cleansing and women use it chiefly to beautify the skin and for thinning hair. Both men and women use it as a dentifrice and men use it for many other purposes. Transcribers smooth books with it. Physicians mix it with substances that produce flesh. When wine workers put in it casks of new heating wine the heating ceases immediately. The drinkers in a drinking contest take a powder of pumice but Theophrastus warns that this is a dangerous practice unless they become satiated with the im­mense draught. Physicians prefer that which is white, rather light, porous, harsh, fragile and free of stones.
Finally I shall discuss the remaining stones—those to which we have given names which come from the fact that when thrown into a furnace they liquify with ease and flow freely. There are three genera of these, one similar to transparent gems and a second that does not resemble gems. The latter is not transparent as a rule, rarely partially so. The former is found in small quantities in silver and other mines. The latter is found in veins characteristic of the mineral and often in abundance. Material of the third genus is used in making glass although glass can be made from the other two genera. Small pebbles of the first genus are not only trans­parent but brilliant and with the same colors as those found in gems. Some of the pebbles resemble quartz, others smaragdus, prase, sapphire, amethyst, hyacinthus, carbunculus, chrysolithus and other gems. However they are markedly different from gems in degree of hardness. If we
Book V about lodestone, hematite, geodes, hematite, selenite, lapis secularum, asbestos, mica Page of 251 Book V about lodestone, hematite, geodes, hematite, selenite, lapis secularum, asbestos, mica
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