ORDER VI. PARATOMOUS AUGITE-SPAR. 273 



White variety. Leek-green variety. Black variety, 



analysed bj Bonsdorf. by Rose. by Rose. 



Silica 54-83 54-08 53-36. 



Lime 22-19 23-47 22-19. 



Magnesia 18-55 11-49 4-99. 



Alumina 0-28 0-00 0-00. 



Protoxide of Iron 0-99 10-02 17-38. 



Oxide of Manganese 0-00 0-61 0-09. 



Loss by heating 0-32 0*00 0-00. 



It may be considered as a bisilicate of lime and magnesia, 

 in Avhich part of the bases are replaced by protoxide of 

 iron, part of the silica sometimes by alumina, which, in the 

 conch oidal Augite from Sicily, amounts to 16-5. Before the 

 blowpipe it melts pretty easily, and emits a few bubbles ; 

 it finally yields a glassy globule, more or less intensely co- 

 loured by iron. It is readily dissolved by borax. Several 

 varieties of the present species have been obtained by way 

 of fusion. Black crystals are not unfrequent among the 

 slags from the iron furnaces in Sweden. They consist of 

 bisilicate of iron. A white variety in perfect crystals has 

 been obtained by Messrs BERTHIER and MITSCHERLICH, 

 when mixing silica, lime, and magnesia, in the necessary 

 proportion, and exposing this mixture in a charcoal crucible 

 to the heat of the Sevres porcelain furnaces. Many va- 

 rieties of Pyroxene, if melted and then allowed to cool 

 slowly, crystallise and assume an appearance little different 

 from what they had before. 



3. Paratomous Augite-spar occurs in imbedded crystals, 

 in various kinds of rocks, in basalt, lava, &c. ; also in beds 

 in older rocks, both in crystals and compound massive va- 

 rieties ; it enters into the regular mixture or composition 

 of several rocks, as the pyroxene rock, some varieties of 

 greenstone and basalt: it likewise is found in veins tra- 

 versing primitive rocks. Foliated, conchoidal, and common 

 Augite are found in the first kind of these repositories ; 

 granular Augite, Coccolite, and Sahlite occur in the second, 

 and are associated with ores of iron and titanium, with 

 hemi-prismatic and prismatoidal Augite-spar, several species 



VOL. II. 



