PHYSIOGRAPHY. 37 



Mesotype. 



1. Before the blow-pipe, it loses its transparency, and melts into a 

 glassy globule : the radiated varieties exfoliate, and the compact ones in- 

 tumesce. They are with difficulty soluble in borax. Some of them as- 

 sume by heat, faint degrees of opposite kinds of electricity on their oppo- 

 site ends, and become positively electric by friction. 



2. Analysis. 

 By GEHLEN & Fucus. By BERZELIUS. By SMITHSON. 



3. The general repositories of this species are the vesicular cavities 

 of amygdaloidal rocks. It occurs associated with Analcime, Chabasie, 

 and Calcareous Spar. 



4. The most distinguished localities are Iceland, Scotland, the Faroe 

 Islands, the Isle of Bourbon, Auvergne and Tyrol. It also occurs 

 abundantly in the basalt of the Giant's Causeway. The variety Na- 

 trolite, and which is of a yellowish grey color, is found in a porphy- 

 ritic rock near Lake Constance ; also at Klingstone near Hohentweil in 

 Swabia. Mesotype, with the exception of one localitiy in Nova Scotia, 

 is a rare mineral in North America. It is met with, however, in small 

 quantities, in the trap of New England, and rarely in seams between 

 Hornblende and Gneiss. The most interesting specimens in the first 

 mentioned rock, occur at Cheshire, (Conn.) ; and in the latter, at Wash- 

 ington, in the same state. 



METAXITE. 



Massive : composition columnar, in extremely thin individuals ; 

 impalpable. 



Lustre silky. Color greyish white. Translucent on the edges. 

 Shining in the streak. 



Hardness (scale of BREITHAUPT) = 3-0 ... 4'0. Sp. gr. = 

 2-520. 



VOL. II. 4 



