352 T. S. Hunt on Algerite. 
From the square form of the prism Mr. Dana has suggested 
that Algerite may be a result of-the alteration of scapolite from 
which species however it differs widely in composition; while 
the latter affords from 13 to 24 p. c. of lime, and from 
soda, Algerite contains neither lime nor soda, but 10 p. ec. of pot- 
ash, so that the change must have consisted in the removal of 
lime and soda, and the substitution of magnesia, water, and a 
large amount of potash, which reactions, especially the replace- 
ment of one alkali by another, seem very questionable. As scap- 
olite has not yet been found with this mineral, it would have 
been better to regard algerite as derived from the alteration of the 
associated idocrase, a process which presents less difficulty to the 
chemist than the other. It may fairly be questioned whether 
the extreme views maintained by some, with regard to the altera- 
tion of mineral species, do not tend to discourage mineralogical 
chemistry, and to embarrass the science with groundless hy- 
potheses. ; 
In support of the view that Algerite is an altered scapolite, 
Mr. J. D. Whitney has given at page 296 of this volume, the 
results of his examination of the mineral. He observes of the 
material selected for analysis, that “after the ignition it was noticed 
that portions of the ignited mineral remained nearly unaltered in 
appearance, while the larger part acquired a brick-red color, and 
on examination with the microscope was seen to contain smal 
silvery scales apparently of mica. As only a small quantity could 
be used for analysis, the results can be relied upon only as ap 
proximatively correct.” p. 208: He gives the following as the 
result of his analysis: Silica 52-09, alumina 18°63, phosphate of 
lime 8-22, carbonate of lime 4-41, water 6:68, loss, potash and 
soda? 9-97 = 100-00. | 
Had the analysis of such a compound agreed with my own, I 
might have had reason to doubt the results of Mr. Crossley and 
myself. Since reading Mr. Whitney’s remarks I have exam) 
several crystals of Algerite for phosphate of lime, by digesting 
their powder with heated hydrochloric acid, and testing the soln: 
tion with molybdate of ammonia; this delicate reagent indicated , 
the presence of traces only of phosphoric acid. The ‘apparently 
pure calcite in which the crystals are imbedded, gives a more G& 
cided reaction, and traces of this acid are seldom wanting eve? 
in feldspars and tourmalines. While, therefore, we do not qgtles- 
scapolite. urther examinations of the mineral may throw oe” 
light upon the variations in the proportions of water and magne>™™ 
Montreal, C. E., March 7th, 1854, re aie 
