352 The American Geologist. December, iwm 
of the original pyroxene, whose cleavage lines have thus been 
preserved occasionally (See plate XII, figure 21). 
Calcite is abundant in the andesine and even in the pennin- 
ite. It is in irregular masses showing twinning and cleavage 
parallel to the rhombhedral faces. 
Bowlingite preserves the irregular form of the primary 
olivine. (See plate XIX, figure 2.}^.) It is now nearly amor- 
phous, and only feebly birefringent. The pleochroism is noi 
sensible, but the color in various parts varies from brownish 
yellow to yellowish green. The refringence (N) seems to be 
practically equal to //g of cakite. 
Epidote occurs rarely in irregularly automorphic, small 
crystals. 
A sericitic mineral is abundant as a decomposition product 
of the andesine, and the chemical composition of the rock ren- 
ders it possible that it is paragonite rather than muscovite. 
The mineral is fibrous or lamellar in habit wdth a refringence 
higher than that of andesine, and birefringence at least .031 
(Mg — Zip. ) The elongation is positive, with extinction sensi- 
bly parallel. 
The chief feature of the chemical composition is nat- 
urally the high per cent of silica; the amount of titanium is 
very noticeable; it was evidently originally in the pyroxene 
and magnetite (?), and is now in the form of rutile. 
I. 
SiOa 56.60 
TiO. 1.59 
AI0O3 17.84 
Fe203 2.55 
FeO 4.09 
MnO Trace 
MgO 3.16 
CaO 6.28 
Na.O 4.45 
K.O 45 
H.O 3.20 
P.O, 14 
100.35 
Sp. Gr 2 . 36 
-2.41 
I. Quartz gabbro (854G) from near Little Saganaga lake. No 
appreciable BaO nor SrO; Fl and CO2 not determined. 
