TABLE IX. 
Colors of 
polarisa- 
tion 
Color and 
inex of 
fraction . 
Structure. 
Association 
Inclusions. 
Alterations 
Occurrence 
Remarks. 
More bril- 
liant than 
augite. 
In sections 
colorless, 
rarely 
green. 
Strongly in 
relief. 
,1^^1.678. 
Surface of sec 
tions rough, 
changes in the 
crevices to red 
dish, brown- 
ish, or green- 
ish serpentine 
and has pico 
tite inclusions. 
Either well 
defined crys 
tals or frag- 
ments or ir- 
regular grains. 
With oliv- 
ine, plagi- 
oclase, ne- 
pheline, 
leucite, 
horn - 
blende, 
and bio tite 
Almost 
never with 
primary 
quartz or 
orlhoclase 
Rather 
poor, aside 
from mi 
nute pico 
tile octa- 
hedrons, 
glass and, 
more rare- 
ly, fluid in- 
clusions, 
magnetite 
Usually 
into ser- 
pentine, 
also into a 
brown, fi- 
brous ag 
gregate. 
Pseudo - 
morphs of 
calcite af 
ter olivine 
in picrite. 
Formation 
of limon- 
ite. 
As prima- 
ry essen 
tial compo 
nent o( all 
basic rock. 
In olivine 
stone and 
picrite, 
melapyre, 
olivine- 
gabbro, ol- 
ivine no 
rite, oliv- 
ine di’base 
Also in cer 
tain mica 
ceous por 
phyries. 
Distinguished 
Irom quartz in 
isotropous 
sections, from 
zoisite by crys- 
talline form 
(not in nee- 
dles) and col- 
ors of polari- 
zation, from 
augite by 
cleavage, from 
sanidine by 
rough surface 
and brilliant 
colors of po- 
larization. 
figureSs double refractive positive, 
bisectrix (-]-) in 0. 
Very bril- 
liant 
About as 
in musco 
vite. 
1 
1 
Light or 
dark yel- 
lowish 
brown, 
strong re- 
lief. 
I. ,66. 
In exceeding 
ly slender 
long needles- 
often numer 
ous or lelted 
in parallel 
masses in 
quartz, cor 
dierite. etc. 
With 
quartz or 
thoclase, 
biotite, 
and mus- 
covite. 
Very poor; 
fluid in- 
clusions. 
As prima- 
ry, acces- 
sory com 
ponent of 
crystalline 
slates; rare 
Distinguished 
from zoisite 
by double re- 
fraction and 
])olarization 
colors, from 
andalusite by 
double refrac- 
tion and 
cleavage. 
Primary 
accessory 
in crystal- 
line slates, 
particular- 
ly mica 
schist 
As above. 
Light or 
dark 
brown. 
( 3 p= 
1,7526. 
Large and 
small crystals, 
characterized 
by many in- 
clusions. 
With 
quartz, or- 
thoclase, 
mica, and 
garnet. 
Minute 
quartz 
grains, bi- 
tumen, 
specular 
iron. 
Easily distin- 
guished by 
pleochroism. 
in basic 
p’rphyritic 
erup lives 
as essential 
and acces 
sory. With 
olivine 
stone. 
Rarely in 
quartz - 
bearing 
rocks, as 
quartz por 
phyry,dia- 
ba.'-e por- 
phyry. also 
in gabbro 
and norite. 
Distinguished 
from olivine 
by fibrous 
structure par- 
allel to c. It 
does not occur 
in minute nee- 
dles as si lima- 
nite. Diflers 
from the fal- 
lowing only in 
absence of 
iron. 
Very bril- 
liant. 
Colorless 
to green, 
strong re- 
lief. 
In irregular 
long columns. 
Often coalesc- 
ed parallel to 
c with mono- 
clinic augite. 
With pla- 
^ioclase, 
olivine, 
and mono- 
clinic au- 
gite. 
Very poor. 
Into ser- 
pentine 
with for- 
mation ot 
talc. Into 
basite. 
