BOLE, a hydrous silicate of Alumina, which occurs as an earthy mineral in amorphous masses in various countries, as in Armenia, Saxony, in Tuscany, at Sienna, in Ireland, and in Scotland in the Isle of Skye.
The colour of Bole is various, either yellow, brown, red brownish, or pitch-black. It is dull, has a greasy feel, and adheres to the tongue. Its fracture is conchoidal, yields to the nail, and the streak is shining. When put into water it readily absorbs it, emits bubbles of air, and falls to pieces. The Armenian Bole, according to Wiegleb, sonsists of Silica 63'13 Alumina . 22.67 Iron Loss . 3.20 The Lemnian Bole, called also Lemnian Earth, was anciently an article of Matoria Medics., and kept by apothecaries in small pieces under the name of Term Sigillate : these were impressed on one side with the figure of a goat, &c. According to Pliny it was also used as red pigment.
Klaproth found the composition of this Bole to be Silica . . . . . . . . 66 Alumina . . . . . . . . Oxide of Iron . ..... . 6 Soda . Water . . ..... . 8.5 A trace of Lime and Magnesia . . .
• 98.5 The only Bole at present used is as a coarse red pigment, for which purpose it is calcined and levigated, and vended in Germany under the name of Berlin and English Red.
These earths were formerly employed as astringent, absorbent, and tonic medicines. They might be slightly serviceable as absorbents,
in the same way as putty powder is used in the present day, when sprinkled over excoriations of the skin. Any tonic power which they possessed was due to the oxide of irou, which is now administered in a purer state. These once celebrated articles have fallen into merited disuse : they are still however employed in the East, and occasionally as veterinary medicines in Europe, where earths of a similar kind are found abundantly among volcanic, basaltic, and the older calcareous rocks, and are called after the different countries in which they are found. Those which have less colour are called Bolus alba, are pro cured in Bohemia, Salzburg, &c., and consist of lithemarge, which is formed of silica and alumina with water, and a little oxide of iron. These substances are extensively employed to adulterate articles of food, as anchovies, cocoa, and other things having naturally a red colour. The Bole Armenian must not be confounded with the Lapis Armenius, which is a native carbonate of copper. The Terra Lemnia is sometimes employed to signify the pulp of the fruit of the A dansonia digitata, the Baobab, or Moukey-Bread, which is used as an astringent for the cure of dysentery by the inhabitants of Senegal.