\ 



Made of Lancaster. 59 



with our mineraL the difference not beins more than could 

 be easily accounted for by disturbing causes during crys- 

 talhzation^ to which all the varied and beautiful forms 

 under which this mineral appears must be referred. 

 Haiiy thought from observation of the natural joints of 

 this mineral, that it had an octaedron with a rectangular 



i 



base for its primitive form. This I am disposed to doubt, 

 and refer it at once to the form of Andalusite, which is a 

 right square, or slightly rhombic prism. It is singular 

 that this mineral should have remained so long without 



having been analyzed, and can only be accounted for by 

 the imperfection of foreign specimens, and the difficulty 

 chemists anticipated in its attack. 



Berzelius examined Made before the blow-pipe, and 



gave his opinion that it was probably a suhsilicate of 

 Alumina^ a result which I have since proved by the 

 analysis accompanying this article. 



After waiting in vain a long time for some chemist to 

 make an examination of this stone, I at last determined to 

 set the question of its composition and nature at rest, by 

 analyzing it. Having enjoyed opportunities of procuring 

 fine and perfect specimens of the mineral during my resi- 

 dence of three years in the country where almost every 

 rock in the fields contained them, I made a plentiful col- 

 lection of all the varieties which this mineral presents. 



For analysis I took a Made from a dark, bluish-black, 

 micaceous clay slate from Lancaster, similar to fig. 9, and 

 havbg carefully freed it from the surrounding matrix, I 

 dissected out the black, rhombic prism fi-om its centre, as 

 foreign to the crystal. The specific gravity was found to 

 be equal to 3.03. Hardness equal to that of Andalusite, 

 or = 7.5 of the scale Mohs. Before the blow-pipe it is 

 infiisible and becomes white. It dissolves with great 

 difiiculty in glass of borax, and the glass had a yellowish 



