378 =B. K. Emerson—Didbase intersecting Zinc Ore. 
The normal constituents of the rock are labradorite, augite, 
biotite, apatite, and probably magnetite, though one cannot well 
distinguish the latter ingredient from the franklinite. The 
shows auliple twinning with extinction at 10° on either side 
of the twinning plane, which would indicate Sangha and 
it often combines with this a second twinning at right angles to 
the first. Another portion shot through with brightly polari- 
zing scales of muscovite resembies a decomposing elzeolite. - 
periments with regard to gelatinization gave oe results, 
from the presence of so much zinc silicate, but so ph ptt 
which did not seem to be willemite were removed be 
The abundant scales of biotite are with great frequency 
pierced by unusually large regular prisms of apatite, and de- 
composition has attacked some crystals at the edge, and fol- 
oe in on certain layers has changed them into an ag 
common oie augite, sod in ester) instances gistoae large 
fragments of willemite and franklinite, or willemite and pyrite, 
and are also surrounded by a greenish zone of equable width 
which shows aggregate polarization, and consists of willemite 
In other varieties of finer grain, the elongated crystals of 
augite, and plates of red mica similar in shape and size to 
these, are more abundant and fill the field in peiculats arrange- 
over a gray or greenish gray semi-opaque substance, made up 
of scales and irregularly rounded particles, is gathered in great 
quantity around these crystals so that they are often almost 
wholly Aegis thereby, and look like acu worms in their 
eases. Thi e seat of very abundant effervescence when 
the slide is ciated with acid, but is only partly removed. 
The feldspathic constituent appears here “ as a colorless 
background, but more sparingly, and it is even more decom- 
posed than in the coarser rock. It differs fier this only in 
St pre in abundance straight acicular ee oo which are 
abundant also in the elongate augite crysta 
The finest grained black rock three Paeeseh from the contact 
