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Book VII marbles, gems in rings and other applications

Book VII marbles, gems in rings and other applications Page of 251 Book VII marbles, gems in rings and other applications Text size:minus plus Restore normal size   Mail page  Print this page
BOOK VII
161
tain named for virgins, the other behind the shrine of St. Nicholas. It may be gray, black, liver-colored, yellow, etc., but these are worthless.
This rock varies in hardness. The Chemnitz material from the oblong mountain is soft, as is the material from the red quarries of the Pallien-ians, Fidenae and Albans. Some is moderately hard as that from the deep quarry behind the shrine of St. Nicholas and the quarry in the woods to the right. This rock was used to build the famous monastery of St. Bene­dict on a small mountain outside the town. The Tiburtian, Amiternian and Soractian quarries have produced this same type of rock. That from the mountains near Mulde between Penica and Roseburg is hard. The temple of Cosus under the sovereignty of Anhalt is made from blocks of a very hard rock, in fact it is so hard it can only be dressed with iron tools and even then only with the greatest of difficulty. This genus, especially when it is soft or moderately hard, usually contains impurities. Sometimes it contains marl that makes holes since the marl falls out when the stone is dressed. Sometimes it contains flint, especially black flint that tends to break from the rock when struck with a hammer and thus make the surface uneven. Sometimes it contains small pebbles similar to gems and although these appear, at first, to enhance the beauty of the stone, during dressing these tend to drop out leaving holes. These can be observed in Elboganun and especially in the walled city of Herzberg.
The very white rock of Megara and other softer varieties contain ma­rine shells throughout and for that reason are called lapis conchites.16 This rock was used, according to Pausanias, in the monument of Phoroneus and in many buildings in the city of Megara. The same genus is found in Thessalia, Haemon, Macedonia, and the mountains of Calabria. Similar rocks quarried near Paris often contain snail shells. Recently a rock was quarried that carried an impression similar to a crown of laurel.
The soft rocks can be dressed with ease with an iron tool but the hard rocks can be dressed only with the greatest difficulty even after they have been left exposed to the air for some time. The moderately hard rocks are dressed with moderate ease. When the soft varieties are exposed to the weather they crumble and dissolve in the rain while the ice and frost break them into small pieces. Some cannot stand the heat of the sun and near the ocean they crumble because of the salt air. In protected places, how­ever, they can sustain heavy loads. The moderately hard rocks sustain heavy loads in exposed places and withstand rain and cold but break up in a fire. The hard stones are not even injured by fire. Copper workers use this genus to make the appropriate molds for casting molten copper. Some varieties are soft and easy to work and still withstand fire and these are the ones most suited for molds. Some rocks, dark gray in color, are found in Hesse and are worked into all types of molds for casting differ­ent metals. The same species is found in Siphnos and in Italy near Como
Coquina and coquina marble.
Book VII marbles, gems in rings and other applications Page of 251 Book VII marbles, gems in rings and other applications
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