210 GEOLOGY OF OLD HAMPSHIRE COUNTY, MASS. 



a millimeter across, often twinned and well terminated, of red-brown color, 

 and with shining faces. The}" ])roject in every direction into the muscovite, 

 and have been plainly mannfactured from the material of the chiastolite ^r>y 

 some second metamorphism. The muscovite gave deep blue with cobalt, 

 and a purple flame when fused with gypsum, and fused with difficulty to a 

 white enamel. It gave the axial divergence of muscovite. The staurolite, 

 measured with reflecting goniometer, gave gc PA cc- Prrl2i)°. oo PA 

 00 PQcrrll5°ir, and twins after | P 06 , could be determined optically 

 under the microscope. 



The andalusite crystiils are orange-yellow under the microscope, but 

 a central portion with boundaries parallel to the surface, even when that 

 surface is plainly one of fracture, is colorless in most cases and has a soft, 

 slightly wavy striation, which a high power shows to be due to the presence 

 of an immense number of stout tubular bodies, slightly reddish, with 

 rounded ends, often slightly twisted and varying in diameter; at times, 

 indeed, passing into formless bodies. They are so numerous as to give the 

 rock a spongy appearance, and are parallel to one another and to the verti- 

 cal axis of the staurolite. They are 0,025™"' long, 0.005""° across. Being 

 placed parallel to the axis of the inclosing mineral, they extinguish with it; 

 but in diagonal position the larger ones show color for themselves, and they 

 are probably quartz. Many sections of the staurolite are broken up into 

 separate fields from twinning, and the rods have a separate direction in each 

 of these fields.' 



The rock contains, also, groups of small garnets. It is a biotite- 

 muscovite-schist. In a quartz-muscovite background many long-notched 

 blades of a dark-brown liiotite and much coaly matter are arranged in a 

 pseudo-fluidal structiu-e and wrap around the chiastolite crystals. 



' Lassanlx, Ueber Staurolite: Tschermaks mineral. Mittheil., Vol. Ill, 1872, p. 173, pi. 3. Compare 

 the uncolored figures where the rods are stouter and more distant than here. 



