Mineraloffical Notices. 499 



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solved out, leaving the form of the crystal unaltered, and the 

 edges as sharp as ever. Their appearance before the micro- 

 scope, after the loss of the sulphate of soda, is that of snowy- 

 white, fine granular sulphate of lime (alabaster). From 15 

 grains of this Glauberite, I have obtained 6^ grains anhydrous 

 sulphate of soda, and do not doubt that the whole quantity 

 might, with care, be extracted. If some forms of these ala- 

 baster crystals had been first found and analyzed, they would 

 have been pronounced to be pseudomorphous forms of an un- 

 known mineral, of which sulphate of lime had taken the place. 

 Now, if the action of the solvent powers of various chem- 

 ical solutions, as well as those of the gases which can be held 

 by water, be studied with care, the natural decomposition of 

 many minerals, as well as their replacement by other sub- 

 stances, in what are called pseudomorphous forms, will be 

 very much illustrated. 



PYRRHITE. 



Prof. J. W. Webster, of Harvard University, has lately re- 

 turned from the Azores, and brousrht with him some interestinor 

 minerals, several of which he has most kindly placed in my 

 hands ; amongst others, a beautiful Arragonite, at first sight 

 much resembling the Needlestone. 



He also favored me with two small specimens of a feld- 

 spathic mineral, probably albite, on which were several 

 extremely minute but beautiful octohedral crystals, of a deep 

 orange to a wine-yellow color, the smallest transparent, the 

 largest translucent on edges. 



At first, I considered this a new mineral, until, on com- 

 paring it with the account of Pyrrhile, in Jameson's Edin- 

 burgh Journal, vol. xxix., the resemblance struck me. I 

 therefore sacrificed these crystals to the blowpipe ; they gave 

 the followincr indications : — 



The minutest transparent crystals changed immediately, in 

 the reducing flame, to a deep, dull indigo blue, perfectly dis- 

 tinct ; the edges then rounded, and, after considerable ex- 

 posure, fused without intumescence ; on the application of 



