Brush and Dana—Danburite from Russell, N.Y. 118 
and in part massive. The crystals vary from those which are 
very minute to others which are of considerable size. The largest 
isolated crystal has a length of 4 and a width (macrodiagonal) of 
24 inches ; some of the groups are really grand in their propor- 
tions. The massive mineral can be obtained in large blocks ; 
it shows brilliant luster, is quite unaltered, and almost entirely 
free from admixed species. The most striking point in rega 
to the crystals is their similarity to crystals of topaz; so close 
is this resemblance that the specimens, if not examined too 
critically, might be handled many times without a suspicion 
that they did not belong to that species. It will be shown 
below that this resemblance extends beyond the mere external 
Description of crystalline form.—The crystals are uniformly 
prismatic in habit. They are commonly attached by one ex- 
tremity of the prism so that only the other end is terminated ; 
occasional crystals, however, have been observed with termina- 
tions alike at both extremities, and hence it is not hemimorphic. 
The general range of form in the crystals will be gather 
from the accompanying figures; figures 1, 2, 3 and 4 show 
some of the more common and simple forms, and figures 5, 6 
and 7 are others more highly modified. It will be noticed that 
proved by the so examination, since the three axes of elas- 
