MINERALOGY. 437 



mountains ; used for polishing serpentine, etc. Surface 

 of fracture fine and even. H. = 2.5. G. = 2.4. 

 Soapstone resembles it, but is softer. 



Fuller's Earth is a white, gray, green or red earth, 

 having a soapy feeling ; slightly adhesive on the tongue. 

 Fracture uneven ; structure sometimes compact, at others 

 laminate, with a shining, oily streak. It falls to pieces 

 in water, but absorbs oil or grease of any kind. Found 

 in Germany, England, and elsewhere. It was formerly 

 used by the fullers for removing the grease from woolen 

 cloths, for which office its faculty of absorbing oils and 

 rejecting water peculiarly fitted it. G. = 2.19. 



Bole. Luster weak, opaque, translucent, earthy. 

 Color white, brown, yellowish, reddish. Feels greasy; 

 fracture conchoidal ; streak shining. Adheres to the 

 tongue ; bursts and falls to pieces in water, and after- 

 wards gradually crumbles into fine powder. Found in 

 basaltic, and clefts of other igneous rocks in Silesia, 

 Bohemia, and Upper Italy. Bole, also called Terra 

 Sigillata, is employed for various purposes, as polishing 

 material, cement, or plaster, bowls, cups, etc., and Turk- 

 ish pipes. H. = 2.0. G. = 1.9 to 2.0. 



THIRD ORDER. 

 MAGNESIA COMBINED WITH ALUMINA. 



I. Talc Family Aluminates of Magnesia. The 

 most conspicuous of this family is 



The Spinel Balas Ruby. Occurs only as a crystal, 

 translucent, often transparent ; luster vitreous. Color 

 generally red, but passing into blue, green, yellow, or 

 dark brown. H. = 8.0, G. 3.4 to 3.8. The red spinel 



