126 



EARTHS. ARGILLACEOUS. 36, Bafaltcs. 



26. BASALTES. Confiding of a large proportion 

 of filica, with a lefi'er proportion of alumina and 

 . oxyde of iron;, and ofttn a little lime, magnefia, 

 oxyde of manganele and foda: opake, inconfpi- 

 ciioiis, meagre, generally becoming greyifh when 

 rubbed with a knife, breaking into indeterminate 

 fragments, mouklering in the air into argil: not 

 effervefcing with nitric acid, melting before 

 the blow-pipe iuto a black glals attiaded by the 

 magnet. 



^chiitcius. Black, of a flaty texture. 



Found in bafaltine mountains on the Rhine, and in the neigh- 

 bourhood of G(J//;;;^v«, coiijnioaly abounding in particles of 

 Olivin. 



columnarii^ Of a dull colour, compact, hardifh, tenacious, fpontancr 

 oufly breaking into prifmaiic granular fragments. 



Bafahes. Baum. miner. 1. p. 220. 



Baia1te.s figura co]umn2*-i. Wall. fyfl. I, />. 3 19. «. 9. » 



Figurate Trap, Bafalt. Kir^w an miner. \. p 23 1. 



Balalt. SchmeiJJer tnin, 1. t. 185. Thomfons chem. 3. p, 575. 



Found in various parts of the Brit-Jh Iflands, particularly in 

 Staffa \n Scotland, and the dances Caufe'way in Ireland, in the 

 South Sea IJl:?jds, Sicily, Italy, France, and many parts of 

 Europe, generally forming the bafe of mountains, of a co- 

 lumnar ihape, rtraight or curved, perpendicular or inclined, 

 rarely parallel; the diameter of the columns from 3 inches to 

 3 feet, (ometimes vviih tranfverfe fcmifpherical joints, in 

 which the convexity of one is inferted into the concavity of 

 the other; their form is pentangular, hexangular, or o6i an- 

 gular, rarely triangular, or quadrangular : colour blueiih or 

 grccnifh-black, or dark greyifti-blue, varioufly interfered with 

 veins of whiie'calcArcous Ipar, and often the impreffi^ns of 

 various folhle bodies and fhrubs: they are rather hard and 

 dilhcult to break, feel harfti, and found under the hammer: 

 texcure earthy : Iradure uneven ; ftreak afhy-grey : fpecific 

 gravity from 2,8&4. to 3,000. a fpecimen fcom Staffa con- 

 tained fi'ica 44. alumina 16. oxyde of iron 16. lime 9. 

 water 5. foda 4. muriatic acid 1. Kennedy, 



fyvamidalii Of a dull colour, compadf, fpontaneoufly falling into py- 

 ramidal fragments. 

 Hacqust Chem. 'Journ. 1788, I. p, 522. 



Found in the mountains o^ Bohemia, mzr JvJJt^, in elongated 

 3-fidcd fragments; and in Hungary^ near Schemniz and Crem' 

 nizj in 4-fided fragments. 



