ORDER vu. EHOMBOHEDEAL CORUNDUM. 303 



compact Felspar. Some varieties have been discovered 

 imbedded in octahedral Iron-ore and macrotypous Lime- 

 haloide, and seem to occur in beds. Those compound va- 

 rieties of which the original repository has been ascertain, 

 ed, occur in a bed of talcose slate, contained in mica-slate. 



4. The finest varieties of Sapphire come from Pegu, 

 where they occur in the Capelan mountains near Syrian. 

 Some have also been found at Hohenstein in Saxony, at Bi- 

 lin in Bohemia, at I*uy in France, and in several other coun- 

 tries. Corundum occurs in the Carnatic in the East Indies ; 

 Adamantine-spar in the neighbourhood of Canton in China 

 and the coast of Malabar. In St Gothard red and blue va- 

 rieties of the present species occur in Dolomite. Those 

 from Gellivara in Sweden, imbedded in octahedral Iron- 

 ore, are of a yellowish-white colour. Emery is found in the 

 higher part of Saxony, in the mountain called Ochsenkopf 

 near Schneeberg, and is of a dark blue colour, inclining to 

 grey ; it approaches to the appearance of blue Corundum, 

 whenever its individuals are of considerable size. In the 

 island of Naxos T and several other islands of the Greek ar- 

 chipelago, also at Smyrna, Emery is found in large boul- 

 ders on the surface of the earth mixed with other minerals. 



5. The pure and transparent varieties of rhombohedral 

 Corundum, if finely coloured, are in great estimation as orna- 

 mental stones. The red varieties are most highly valued, 

 and go by the name of Oriental Ruby, the violet-blue are 

 called oriental Amethyste, the green oriental Emerald, the 

 yellow oriental Topaz, and the blue oriental Sapphire. As- 

 teriais a variety of Sapphire, not perfectly transparent, and 

 shewing a starlike opalescence in the direction of the axis 

 if cut round. Much use is made of Corundum and Ada- 

 mantine-spar, particularly in India and China, for cutting 

 and polishing steel and gems, and it is said even of dia- 

 mond, ^which has given occasion to the name of Ada- 

 mantine-spar. Yet they are much inferior in this respect 

 to the powder of diamond ; and European artists therefore 

 make use of the latter for cutting the diamond, and for ex- 



