2/6 The Americmi Geologist. November. 1900 
which by analogy with mesolite will be considered m(iio) and 
/.(no). 
The hardness is 4.5 to 5.; single fibers are very fragile; 
masses are tough especially across the direction of the fibers. 
The specific gravity determined with tetrabromide of acety- 
lene and the Westphal balance is 2.215. Pseudomesolite fuses 
easily (fusibility about 2.) with no appreciable change of vol- 
ume to a white porcelain-like mass. In the tube it gives 
water. 
The color of pure pseudomesolite in fibrous mass is porce- 
lain white; separate fibers are transparent and colorless. But 
it is often colored in shades of pink, and more rarely green, 
in bands perpendicular to the elongation of the spherulitic 
masses. These bands alternate with bands nearly pure white. 
The pink bands are undoubtedly due to the presence of fine 
particles of hematite ; the green bands have a dissimilar origin 
and are supposed to be due to the presence of iron protoxide 
replacing some other element (Ca?) in the chemical composi- 
tion. 
The lustre is usually rather dull, subvitreous to pearly. In 
thin section the perfectly fresh unaltered part is very trans- 
parent and colorless; but the larger part is only translucent, 
being nearly amorphous, and then may be called cloudy white. 
The refringence is very low, always inferior to labradorite ; 
there is a total absence of relief. The birefringence is some- 
what weaker than that of mesolite, and is comparable to that 
of apatite, but probably weaker. Pseudomesolite is biaxial 
and positive with a very small optic angle: ;/m and //p are 
therefore practically equal. The elongation of the fibers is 
always positive , while the extinction angle in sections parallel 
to the elongation reaches a maximum of at least 20° ; it is 
sometimes near 0°. Therefore /ig is approximately parallel 
to the elongation ; the position of the other two indices relative 
to the faces of the vertical zone cannot be stated; it is only 
known that the extinction in transverse sections is sensibly 
parallel with the diagonals of the squares or rhombs formed 
by the faces /(no) and /;/(iio). Such sections between crossed 
nicols show a poorly centered bisectrix, which is positive, but 
the birefringence (//m-z/p ) is so weak that even with the thick- 
est sections the interference fieure is indistinct. 
