OTRODUCTION. 



To render the present Catalogue of Minerals more than a mere 

 enumeration of names, the forraulai expressing the chemical com- 

 position of the mineral and the system in which it crystallizes, as 

 far as at present understood, have been given. The classification 

 adopted is Dana's, as published in the fourth edition of his 

 Mineralogy. Some species that have proved not to be well 

 founded have been omitted, and many since published have been 

 added. Of these latter species, some must be considered as having 

 only a provisional place in the series, and it is probable that others 

 will ultimately be dropped altogether. In making the additions 

 and corrections, the Supplements to Dana's Mineralogy, which 

 have appeared from time to time in Silliman's Journal, have always 

 been consulted, and the most probable formulte, as deduced by 

 recent investigations, have been selected. In a few instances a 

 change has been made in the place of a species where a more 

 thorough examination has thrown light upon the true nature of 

 the mineral or where it has been found that the system of crystal- 

 lization had previously been incorrectly given. Fmijasite, p. 19, 

 was formerly considered as dimetric, it has lately been proved to 

 be mono metric, and it has therefore been placed among the mono- 

 metric zeolites. The formula for Euclase is the one given by 

 Rose ; Damour's analysis gave water, and the formula 2Se Sil + 

 3X1 Si| -1- n. Ilammelsberg has recently discovered the existence 

 of protoxides in Stanrotide, and proposes as a general formula 

 (fi, W) + §i°. In the formula for Opal, water has not been written, 



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