TABLE II. 
rent in thin Sections. 
{Sec also amorphous-minerals^ Opal and Hyalinamorph) 
Strticture. 
Association. 
Inclusions. 
Alteraiio7is . 
Occurre7tce. 
Remarks. 
Intimately 
united 
with feld 
spar and 
hornblend 
often with 
a colorless 
nucleus 
and red 
cortical 
part closed 
by oxides 
of iron. 
With micro- 
din e augite, 
and mica in 
syenites, with 
sanidin and 
augite in 
Trachytes. 
Fluid inclu- 
sions, gas 
pores. 
Glassy inclu- 
sions, needles 
of augite. 
Becomes tur- 
bid from al- 
teration into 
zeolites. 
As primary 
constituent in 
syenites and 
rarely in au 
gite-trachytes 
as secondary 
product in 
cavities of the 
latter. 
These three 
minerals can 
only be dis- 
tinguished 
with certainty 
by microche- 
mical qualita- 
tive analysis. 
Hauyn may 
be distin- 
guished from 
sodalite by 
the presence 
of the charac- 
teristic need 
les of gypsum 
on evapora- 
tion of the ni- 
tric acid solu- 
tion. Sodal- 
ite is charac- 
ized by its 
chlorine. 
Hauyn and 
Nosean are 
chemically 
difficult to dis- 
tinguish and 
mineralogical- 
ly may be 
united. 
Garnet may 
be easily dis- 
tinguished 
from Hauyn 
by the color 
and insolu- 
bility in acids 
Very often 
with a cor- 
tical part 
colorecl dif 
ferently 
from the 
centre 
which may 
be darker. 
opaque. 
Often col- 
ored by 
iron in the 
fissures 
Chiefly with 
leucite, nephe 
line and au- 
gite. 
1 
Innumerable 
gas pores and 
glass inclu- 
sions ar- 
ranged in 
bands, minute 
black grains 
and needles, 
often regulai- 
ly distributed, 
tables of spec- 
ular iron. 
Alters into an 
aggregate of 
double re- 
fracting need- 
les and fibres 
of zeolite and 
cal cite produ- 
cing a destruc- 
tion of the col- 
or, and by sec 
ondary colora- 
tion by iron, 
a change to 
yellow. 
As primary 
constituent of 
later eruptive 
rocks (those 
containing 
sanidin as 
well as -those 
bearing plagi- 
oclase) such as 
trachyte(rare- 
ly) phonolite, 
leucitophyre, 
tephrite and 
nephelin and 
leucite-basalts 
Occurs also 
frequently in 
volcanic tra- 
chyte. 
Primary con- 
stituent in 
many slaty 
rocks, fre- 
quently in 
granite, rarely 
in trachitic 
rocks 
Primary con- 
stituent of ser- 
pentines. 
Often uni- 
ted with 
quartz or 
feldspar 
in micro- 
pegmatite. 
i 
Usually with| 
quartz, ortho- 
clase, biotite, 
and horn- 
blende. 
Cavities hav- 
ing the form 
of the garnet 
crystal (nega- 
tive crystals) 
Fluid inclu- 
sions, quartz 
grains, rutile 
grains ; often 
in zonary 
jbands. 
Changes on 
the surface 
and in crevi- 
ces to plates 
of chlorite, or 
(more rarely) 
into fibrous 
hornblende or 
augite. 
with olivine 
and augite. 
1 
1 Very poor, 
1 
j 
Very charac- 
teristic are 
zones of au- 
gite fibres ar- 
ranged in 
groups per- 
pendicular to 
the surface. 
