PSEUDOMORPHOUS MINERALS OP NEW YORK. 245 



cases is ascribed by Beudant to the substances which ai'e asso- 

 ciated with the hornblende, as spinelle, Wernerite, &c. 



The limestone which contains this soft hornblende is not, 

 I believe, remarkable for the abundance of spinelle, but a variety 

 of mica is disseminated through it, which is very rich in 

 alumina. 



These crystals have been ticketed pyroxene, zoizite, and 

 lastly, kerohte pseudomorphous of hornblende. The crystalline 

 form, however, is totally distinct from either of the two former, 

 and its chemical composition must remove it entirely from the 

 latter. It is most probably hornblende altered by an intrusion 

 of alumina and the removal of a part of the silica. The con- 

 torted and somewhat fused appearance of many of the crystals 

 clearly point to heat as the general agent by which these changes 

 have been produced. And as gi'anular condrodite and fluor 

 spar are disseminated through the same limestone, may not the 

 condrodite have been formed by the combination of the silica, 

 which these crystals have lost, with the magnesia and the fluor, 

 by the decomposition of the mica ? 



Grayish-green Mineral. 



In the same town, and in the same limestone, there are crys- 

 tals of a grayish-gi-een color, and having the form of long oblique 

 rhombic prisms, with the angles of hornblende. 



The hardness of these crystals scarcely exceeds that of talc. 

 They are sometimes sHghtly translucent. The powder is white. 

 The following are the results of my analysis of a fragment of 

 one of the most perfect crystals, namely : 



Silica, 34.66 



Alumina, 25.33 



Lime, 5.09 



Magnesia, 25.22 



Water, 9.09 



In this case, therefore, there is a little less lime and more mag- 

 nesia than in the preceding. The proportion of alumina is also 

 less, which is made up by water. 



The nature of the changes which have taken place in this 



