SUBSILICATES. 285 



Chiasiolite and made are names given to crystals of ancla- 

 lusite which show a tessellated or cruciform structure when 

 broken across and polished. The above figures represent 

 sections of crystals from Lancaster, Mass. The structure is 

 owing to carbonaceous impurities distributed in the crystal- 

 lizing process in a regular manner along the sides, edges 

 and diagonals of the crystal. Their hardness is sometimes 

 as low as 3. 



Diff. Distinguished from pyroxene, scapolite, spodumene, 

 and feldspar, by its infusibility, hardness, and form. 



Obs. Most abundant in clay slate and mica slate, but oc- 

 curring also in gneiss. Found in the Tyrol, Saxony, Bavaria, 

 etc. ; also in Westford, Mass. ; Litchfield and Washington, 

 Ct. ; Bangor, Me. ; Leiperville, Marple, and Springfield, 

 Penn. ; and chiastolite at Sterling and Lancaster, Mass., 

 and near Bellows Falls, Vermont. This species was first 

 found at Andalusia in Spain. 



Fibrolite. — Sillimanite. Bucholzite. 



Orthorhombic. In long, slender rhombic prisms, often 

 much flattened, penetrating the gangue. i"A/=96°-98°. 

 A brilliant and easy cleavage, parallel to the longer diago- 

 nal. Also in masses, consisting of aggregated crystals or 

 fibres. Color hair-brown or grayish brown. Lustre vitre- 

 ous, inclining to pearly. Translucent crystals break easily. 

 H.=G-7. G. =3-2-3-3. 



Composition. A10 5 Si, as for andalusite, = Silica 36-9, alu- 

 mina 63*1 = 100. Moistened with cobalt nitrate and ig- 

 nited assumes a blue color. Infusible alone and with borax. 



Diff. Distinguished from tremolite and the varieties gen- 

 erally of hornblende by its brilliant diagonal cleavage, and 

 its infusibility ; from kyanite and andalusite by its brilliant 

 cleavage, its fibrous structure, and its rhombic crystalline 

 form. 



Obs. Found in gneiss, mica schist, and related metamor- 

 phic rocks. Occurs in the Tyrol, at Bodenmais in Bavaria ; 

 at the White Mountain Notch in N. H. ; at Chester and 

 near Norwich, Conn. ; Yorktown, N. Y. ; Chester, Bir- 

 mingham, Concord, Darby, Penn. ; in North Carolina ; and 

 elsewhere. Fibrolite was much used for stone implements 

 in Western Europe in the " Stone age ; " the locality whence 

 the material was derived is not known. 



