IS 



1°. In right angled four-sided prisms, acuminated by four 

 planes, whicli are set on the lateral planes. 



2°. In six-sided prisms, which are said sometimes to ex- 

 hibit a tendency to a six-sided acumination. 



3°. In acicular and capilliform crystals, whose regular 

 shape is no longer determinable, and which are, moreover, 

 strongly compressed. 



The crystals are longitudinally sulcated, often very deeply ; 

 are commonly small, and very small, rarely middle sized. 

 The acicular are often fascicularly aggregated : the capilli- 

 form crystals are often in a singular manner reticulated, the 

 interstices forming equilateral triangles: exteriorly, shining 

 and moderately glistening; interiorly, glistening; the lustre 

 adamantine. 



The principal fracture is foliated with a two-fold cleavage, 

 cutting each other at right angles : the transverse fracture is 

 imperfect and minute conchoidal. 



The fragments are cubical. 



It sometimes exhibits slender, columnar, distinct con- 

 cretions. 



Is usually translucent, sometimes only translucent at the 

 edges. 



Hard. i 



Brittle. j,. 



Gives a pale orange yellow streak. -i 



Is easily frangible. 



Heavy, in an inferior degree, about 4, 200. 



OBSERVATIONS. 



