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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
90
DE NATURA FOSSILIUM
friable that it can be pulverized between the fingers. Hard material is burned by the inhabitants of the Harz forest and Thuringia and after being burnt is ground. They then mix this with water and use it instead of chalk since it is more tenacious. The Phoenicians, Syrians and others have all burnt and used gypsum at various times. Irrespective of the origi­nal color it is always white after burning. Since it is glutinous it retains heat within itself for a long time after being burnt as does limestone. In the same manner gypsum is made from selenite (lapis specularis) after having been burnt and this is the best. When burnt gypsum is mixed with water it has the color of milk. When preparing it they pour the water over the powder and stir it with wooden spoons in order to mix it well. They do not use their hands as one cannot stand the heat. Having been wetted, Pliny writes, it is used immediately since it sets and dries very rapidly. It can be crushed and reduced to a powder a second time. If moistened and allowed to stand over night it becomes so hard that an ax must be used to break it. After wetting it a second time with water it can be used to cement rough stones, as a whitewash and in arenas. The small figures for buildings and the images of saints are made both from burnt and wetted gypsum and carved from the natural mineral, especially that which is similar in color to ivory. Pliny writes that Lysistratus of Sicyon, brother of Lysippus, was the first to sculpture the figure of man from this mineral and then cover the figure with wax to free it from any imperfections.6 At Northusa in Thuringia a gray wall has been built from the gypsum that occurs in beds in the vicinity and the wall of the port of Algiers, a town of Mauretania, Africa, is of similar material. Pliny writes that the sourness of wine is reduced through the use of African gypsum. Theophrastus writes that fullers have used this mineral instead of cimolian earth at various times for preparing animal skins. It dries when used as a remedy and has the power of producing a film over any­thing. For that reason it stops the flow of blood when mixed with the white of an egg. Having been burnt and thus made more tenuous it dries more but is less able to produce a film over anything. When drunk it is fatal since it blocks the veins and causes acute constipation.
Selenite (lapis specularis) is related to gypsum.6 It forms from limestone
6 Lysippus was a celebrated metal worker who lived in the latter part of the 4th century, B.C.
6 In modern usage gypsum is a generic name and selenite a specific name given to gypsum occurring in transparent discrete crystals. Agricola uses these names in much the same sense in his writings. Many of the older writers confused gypsum and mica and Agricola is probably the first to clearly distinguish the two minerals. It is interesting to note that in Interpretatio he describes lapis specularis as unser lieben frawen eis-spar. Itali lumen de scaiola. Today the name eis-spath is given to mica and Werner gave this name to sanidine feldspar. The following reference to gypsum is given in Bermannus, page 456,— Naevius. "But you do not recognize gypsum and lapis specularis which you have
already mentioned.
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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