SUBSILICATES. 289 
Chiastolite and macle are names given to crystals of anda- 
lusite which show a tessellated or cruciform structure when 
broken across and polished. The above figures represent 
sections of crystals from Lancaster, Mass. ‘lhe 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 teldspar, 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 Sterlmg 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. /Al=96°-98°. 
A brilhant 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. 
HW. =6-7. G.=3°2-3°3. 
Composition. Al O,;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. 
Dijf. 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 
aoe its fibrous structure, and its rhombic crystalline 
orm. 
Obs. Found in gneiss, mica schist, and related metamor- 
phic rocks. Oceurs 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. 
