Bole, mineral used as a brown and red pigment and medicinally since ancient times. Lemnian soil in particular was highly regarded as a medicine, while that of Sinope served as paint. The former was traded, as it is now, with a seal stamped on it (sealed earth, terra sigillata). Since 1508 the light brown sealed earth from Striegau, later the bluish-grey Saxon seal or miracle earth (teratolite, iron stone marrow) from Planitz near Zwickau was in use. Mineralogy defines bole as a greasy to the touch, faintly glossy isabelline or leather brown mineral that breaks up into angular pieces in water; hardness 1-2, specific weight 2.2 to 2.5. Essentially a water-containing alumina silicate of varying composition, bole is often found in cavities and on joints of basalt, such as in Striegau and Goldberg in Silesia, in the Habichtswald, in the Rhön, in Bohemia, near Siena, as well as in older flood basalt in Sinope and on Cyprus (Cypriot umber). It is occasionally found in serpentine (Frankenstein in Silesia), in limestone, on iron ore deposits (Neuenburg in Württemberg) and on veins of ore (Freiberg).
White bole (bolus alba, kaolinite, China clay), usually a light grey clay or bole, was formerly used as a drying and hemostatic agent and as a putty. Brown bole (brown earth of Siena, Terra di Siena) is used in fresco painting and as a printing ink for brown engravings. Red bole from Sinope and from North Africa can still be observed as a saturated colour in Pompeii. Red bolus (bolus rubra) serves as a paint and is sourced especially from Nuremberg, the finest variety being the Armenian or Oriental bole. Ancient peoples already used leukophoron as an adhesive base for gold on wood, and bole sizing is still used today for wood gilding, gold and silver paper.
Burned yellow bole is traded as English or Berlin Red, it is also used as a putty, for making moulds for metal casting, for vessels and pipe bowls and washed as a polish for glass, metals and stones. See earths, edible, and kaolin.
Source: Meyers Großes Konversations-Lexikon, 6. Auflage 1905–1909