ZOISITE FROM LOWER CALIFORNIA 
BY OLIVER CUMMINGS FARRINGTON 
While at San Diego, California, in the spring of 1905, the writer 
obtained from Mr. Ernest Riall of that city several specimens of a 
radiated mineral, collected by Mr. Riall at the Trace mine, in the 
Juarez District of Lower California. This locality, according to Mr. 
Riall, is situated sixty miles south of the international boundary. The 
accompanying cut shows the appearance of a typical specimen of the 
mineral. It occurs as divergent groups of long, prismatic crystals irreg- 
ularly penetrating a matrix of a white, granular mineral. The length 
of the crystal groups varies from one to three inches. Their form 
is essentially conical, the angle of the cone being about 10°. In coloring 
the cones are pink peripherally, pass interiorly into nearly colorless 
_andatthe center are brownish-gray. Their constitution of numerous 
individual crystals is shown by elongated brilliant surfaces into which 
they readily separate longitudinally, but transversely the cones break 
as units. -The cones as a whole are translucent, but small fragments 
are transparent. No terminal planes can be observed on any of the 
crystals. The longitudinal fragments show roughly prismatic bound- 
aries, but it was found impossible, witha reflecting goniometer, to ob- 
tain satisfactory measurements of the prismatic angles, since numer- 
ous longitudinal striations produce long series of reflections. Besides 
the striated planes, others not striated appear to be cleavage planes | 
to the brachypinacoid. The longitudinal fragments are colorless and 
transparent and show in polarized light extinction parallel to the long 
axis. No pleochroism is observable. The character of the double 
refraction is positive. In convergent light the emergence of an optic 
axis may be seen on such fragments. Sections perpendicular to the axis 
of the cone are colorless and show no pleochroism. Numerous cleavage 
cracks making angles of 53° with each other penetrate such sections. 
‘Between crossed nicols a polysynthetic twinning structure is seen to 
characterize the whole, the field being filled with lamellae in parallel 
position. These lamellae divide into two groups as: regards width, 
the broader being from .1 to .o7 mm. and the narrower from .025 to 
.o12 mm. The broad and narrow lamellae alternate. The direction 
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