ON CRYOLITE. 



467 



It occurs in distinct concretions, which are thin 

 and straight lamellar. 



It is translucent, sometimes inclining to semi- 

 transparent. 



Is soft ; is scratched by fluor-spar ; but it 

 scratches selenite. 



It is intermediate, between sectile and brittle, 

 Is easily frangible. 

 Specific gravity 2.949. 



GEOGNQSTIC RELATIONS. 



It occurs, massive and disseminated, in a mass 

 composed of sparry ironstone, lead- glance, iron- 

 pyrites, and common quartz. The sparry iron- 

 stone is in large and coarse granular distinct con- 

 cretions, and has a yellowish-brown colour inter- 

 nally ; but, externally, is tarnished deep blackish- 

 brown : The lead-glance is minutely dissemina- 

 ted : The iron-pyrites is either disseminated or in 

 small dodecahedrons : and the auartz, which is in 

 very small quantity, is greyish- white, and minute- 

 ly disseminated. 



The sparry ironstone is the predominant fossil 

 in the different specimens ; the cryolite is in a less 

 proportion ; and the lead-glance, iron-pyrites and 

 quartz, are in nearly equal quantity, but form a 

 small portion of the mass. As all these minerals 

 are massive or disseminated, never crystallised, if 

 we except the small, and very few crystals of iron- 



© g 2 



/ 



