Bole, (Gr. a mass), an argillaceous earthy mineral which occurs in amorphous masses of various colors, as yellow, black, brown, and bright red, all derived from oxide of iron. The substance is probably disintegrated basalt. It has a conchoidal fracture, yields to the nail, and the streak is shining. When placed in water it absorbs it rapidly, and falls to powder. It was formerly employed as a medicine for its absorbent, astringent, and tonic properties; the last due, no doubt, only to the iron in its composition. It is still used in India in medicine, and in Europe for giving a color to anchovies and tooth powders, and as a medicine in veterinary practice. Analysis shows it to be a hydrous silicate of alumina, with varying proportions of oxide of iron, and very small quantities of lime and magnesia. It is used as food by some of the native Indians of South America, and the Japanese eat it to induce a thin and spare habit of the body. In Germany bole is calcined, washed, and ground for a paint, and employed to remove grease stains from cloth or wooden floors, and hence called Bergseife, mountain soap.
The paint known as sienna, or burnt sienna, is a preparation of a chestnut-brown variety from Siena in Italy. It is fashioned into pipes by the North American Indians, Turks, and Germans.