EUCLASfi. 



199 



(see the figure.) Other localities are Barre, Fitchburg, 



Goshen, Mass. ; Albany, Norwich, Bowdoinham and Topham, 

 Me. ; Wilmot, N. H. ; Monroe, Conn. ; Leyperville, Penn. 

 The name beryl is from the Greek beryllos. 



EUCLASE. 



Monoclinic. In oblique rhombic prisms ; M : M=115°. 

 Cleavage in one direction highly perfect, affording smooth 

 polished faces. 



Color pale green. Luster vitreous ; transparent. Vsry 

 brittle. H=7*5. Gr=2*9 — 3-1. Pyro-electric. 



Composition: silica 43*2, alumina 32'6, glucina 24*2. Be- 

 fore the blowpipe with a strong heat it intumesces, and finally 

 fuses to a white enamel. 



Dif. The very perfect cleavage of this glassy mineral is 

 like that of topaz, and at once distinguishes it from tourma- 

 line and beryl. It differs from topaz in its very oblique 

 crystals 



Obs. Occurs in Peru, and with topaz in Brazil. 



Uses. The crystals of this mineral are elegant gems of 

 themselves, but they are seldom cut for jewelry on account 

 of their brittleness. 



M 



A 



4 



N 



V 





CHRYSOBERYL. 



Trimetric. In modified rectangular prisms. 

 1 46. M :e=125 5 20'. Cleavage 



not very distinct, parallel to m. 

 Also in compound crystals, as in 

 fig. 2. Crystals sometimes thick ; 

 oflen tabular. 



Color bright green, from a light 

 shade to emerald green ; rarely 

 raspberry or columbine red by transmitted light. Streak 

 un colored. Luster vitreous. Transparent to translucent. 

 H=8*5. Gr = 3-5— 3-8. 



Composition: alumina S02, glucina 1 98= 100. A little 

 ron is sometimes present. Infusible and unaltered before 

 the blow-pipe. 



Alexandrite is a name given to an emerald-green variety 

 i'om the Urals, which is supposed to be colored by chrome, 



What is the form and cleavage of euclase 1 what the color and luster 1 

 How is it distinguished 1 What are its uses? What is the appearance 

 of chrysoberyl? its hardness? its composition 1 What is alexandrite 1 



