280 PHYSIOGRAPHY. CLASS 11. 



A white A green A black Sraaragdite 



var. var. var. from Corsica. 



Silica 60-31 46-26 45-69. 50-0. 



Magnesia 24-23 19-03 18-79. 6-0. 



Lime 13-66 13-96 13-85. " 13-0. 



Alumina 0-26 11-48 12-18. 11-0. 



Protoxide of Iron 0-15 3-43 7-32. Oxide of Iron 5-5. 

 Protoxide of Man- 

 ganese 0-00 9-36 0-22. Ox. of Copper 1-50. 

 Fluoric acid 0-94 1-60 1-50. Ox. of Chrome 7'50. 

 Water and foreign 



substances 0-10 1-04 0-00. 



Before the blowpipe it melts with difficulty, and a little in- 

 tumescence, into a globule which is not clear, and variously 

 coloured by iron or chrome, agreeably to the contents of 

 the specimen. Also in borax it is but slowly soluble. 



3. In its geological relations, the species of hemi-prisma- 

 tic Augite-spar remarkably agrees with that of paratomous 

 Augite-spar. Imbedded crystals of basaltic Hornblende 

 are found like those of Augite, and frequently along with 

 them in basalt and amygdaloidal rocks ; crystals of com- 

 mon Hornblende and of Tremolite, also compound varieties 

 of the latter occur in limestone rocks ; the former likewise 

 in porphyry and granite. Common Hornblende, Actino- 

 lite and Tremolite, particularly the asbestous varieties of 

 the latter, occur in metalliferous beds in ancient rocks, 

 with ores of iron and titanium, with Iron-pyrites, dodeca- 

 hedral Garnet-blende, hexahedral Lead-glance, &c. Com- 

 mon Hornblende also frequently enters into the composi- 

 tion of rocks, as syenite, several kinds of greenstone, green- 

 stone slate, &c. The finest varieties of Actinolite are found 

 in imbedded crystals, or columnar compositions in talc slate ; 

 and capillary crystals of it and of Amiantus line the sides 

 of narrow veins in primitive mountains. Hornblende slate, 

 and certain varieties of common Hornblende, often mixed 

 with rhombohedral Quartz, several kinds of Mica, dodecahe- 

 dral Garnet, Sac. form by themselves beds in primitive and 

 transition mountains. Carinthine occurs in beds included 



