O. A. Derby—Flexibility of Itacolumite. 205 
The block, 6 a, about two meters thick and separated by 
open fissures from its neighbors on either side, is traversed 
near the middle by three cracks. From between two of these 
cracks a prism-shaped mass had fallen out, leaving an open 
space. Water percolating through these 
cracks has opened several concealed 
planes of lamination in the right-hand 
portion (a); while to the left of the 
cracks, although these planes are 
clearly indicated by faint lines of color, 
the stone shows no signs of yielding 
along them, and fragments detached 
with the hammer at 6 do not break 
along the dotted limes more readily 
than in any other direction. At the rock is exceedingly hard 
and not at all friable or flexible, while at a@ it divides readily 
into slabs two or three centimeters thick, crumbles to sand with 
the pressure of the fingers and is slightly flexible. It should 
well in an fine-grained and thin-bedded or laminated pate 
‘te or ordinary sandstone. Further examination will very 
ppbabty show that it is not limited to rocks of any definite 
Orizon or to any well characterized natural division of the 
quartzose rocks. 
