OJNDjrfODITE. 15*7 



chrysolite. — Olivine. 



Trimetric. In right rectangular prisms, having perfect 

 cleavage parallel with the smaller lateral plane. Usually 

 in imbedded grains of an olive green color, looking like green 

 bottle glass. Also yellowish-green. Transparent to trans- 

 lucent. H=s6-5 — 7. Gr=3-3 — 3'5. Looks much like 

 glass in the fracture, except in the direction of the cleavage. 



Corn-position : silica 38*5, magnesia 48-4, protoxyd of 

 iron 11*2, oxyd of manganese 0*3, alumina 0*2. Darkens 

 before the blowpipe but (except certain varieties) does not 

 fuse. Forms a green glass with borax. 



Dif. Distinguished from green quartz by its occurring 

 disseminated in basaltic rocks, which never so occurs ; also 

 in its cleavage. On account of its gangue it cannot be mis- 

 taken for beryl. From obsidian or volcanic glass it differs 

 in its infusibility. 



Obs. Occurs disseminated through basalt and lavas, and 

 is a characteristic mineral of some varieties of these rocks. 

 Has been found in New Hampshire. Boltonite, from lime- 

 stone at Bolton, Mass., is a variety of chrysolite. 



Uses. Sometimes used as a gem, but it is too soft to be 

 valued, and is not delicate in its shade of color. 



CHONURODITE. 



Usually in imbedded grains or small rounded or flattened 

 kernels or nodules in limestone, and apearing brittle. Struc- 

 ture finely granular without cleavage. Color brownish yel- 

 low or brown, sometimes reddish or white, and occasionally 

 black. Luster vitreous, inclining a little to resinous. Streak 

 rarely colored. Translucent or subtranslucent. Fracture 

 uneven. e=a6— 6 5. Gr=3-1— 32. 



Composition: silica 33*1, magnesia 55*5, protoxyd of iron 

 3*6, fluorine 7 6. From New Jersey. Fuses with difficulty on 

 the edges. With borax fuses easily to a yellowish-green glass. 



Dif. As it occurs only in limestone it will hardly be con- 

 founded with any species resembling it in color when the 

 gangue is present. The specific gravity is less than that of 

 tourmaline or garnet, some brownish yellow varieties of 

 which it approaches in appearance ; moreover, it is seldom 

 in crystals, and when so, the faces are not polished. This 



What is the crystallization of chrysolite 1 describe its character ; its 

 blowpipe action ; composition ; occurrence ; differences. Describe 

 cnondrodita. 



