WIGGLKSWOirni: SKRI'KNTINKS OF VKiniONT. 101 
granular, and rarely fibrous. It is gem*rally colorless hut lias occa- 
sionally a light grccnish-ycllow tint, rnfortmiatcly no traces of any 
pseudoinorphic forms arc present, and it is seldom that the grains of 
magnetite are arranged so as to suggest any of the original crystal 
lines. 
Olivine is present in sixteen of the sections, occasionally in large 
prisms, hut more often in gronjjs of roundeij fragments, or scattereil 
small grains, in various stages of alteration to serpentine. In two 
cases the olivine showed a perfect development of cleavage, and in all 
the others only the characteristic irregular fracturing is seen. The 
presence of olixine is of the higluvst imjjortance in determining the 
origin of serpentine. Ecjually interesting, however, is the lack of talc 
in all sections containing oli\ine. 
Monoclinic pyroxene was identified in three cases, and probably 
exists in others. Owing to its method of occurrence it could not 
always be distinguished with certainty from oli\ine. It shows no 
crystal form, but when cleavage is present can be distinguished from 
olivine by its extinction angle. Pyroxene is never present in large 
amounts, but since, like the olivine, it has altered to serpentine, it is 
po.ssible that it was formerly fairly abundant. 
Magnetite occurs in widely \arying amounts, in all the sections; 
sometimes as octahedra, but more often as irregular grains, or aggre- 
gates. Occasionally the arrangement of these grains suggests that 
it is an alteration product from some other mineral; some of it, how- 
ever, is without doubt original. When dolomite is present in the .sec- 
tion, it often surrounds the magnetite. Similarly the magnetite is 
sometimes surrovmded l)y serpentine composed of radially arranged 
fibers. 
("hromite was distinguished in twelve sections, its presence being 
first detected by a very dark brown color in the thinner parts of a 
section. Elsewhere it might easily be mistaken for magnetite e.xcept 
for the fact that in these rocks it usually occurs in larger and more 
irregular masses. Its presence was also establishcfl l)y chemical test. 
Xo talc is present in the sections containing chromite. 
Dolomite is common either as rhombs of varying size, or in more 
massive form; in the latter case it may constitute a very considerable 
part of the whole section. In one or the other of these two forms it 
was seen in thirty-seven sections. It is usually colorless, shows typi- 
cal cleavage, and often contains small grains of magnetite as inclusions. 
The distinction of dolomite from calcite was made bv chemical test. 
