negative. table v . 
Pleo- 
chro- 
ism. 
St r tut lire. 
Associ- 
ation. 
Tuclusions 
Alterafns 
Occurrence. 
Reniarks. 
Like 
rutile. 
With 
quartz, 
ortho- 
clase, 
biotite. 
Very rare in 
granite, quartz 
-porphyry, 
and crystal- 
line slates. 
Scapolite 
seems to fre- 
quently re- 
place plagio- 
claseand to be 
formed by its 
decompositi’n 
With 
sanidine 
sodalite, 
and 
augite. 
With 
quartz, 
plagio- 
clase. 
calcite. 
augite. 
garnet, 
rutile, & 
titanite. 
Poor. 
Fluid in- 
clusions. 
Rutile 
occurs in 
scapolite. 
Confused 
fibrous; 
changed 
into 
calcite. 
Primary ac- 
cessory com- 
ponent, rarely 
in trachytic 
rocks. 
Rare, in crys- 
talline slaties, 
with plagio- 
clase as a 
(secondary?) 
accessory 
component. 
S capolite is easily 
distinguished from 
orthoclase and cal- 
cite by its optical 
peculiarities and 
cleavage. 
Mejonite is recog- 
nized by its crystal 
form. 
Rect- 
angu- 
lar 
longi- 
tudinal 
sect’ns 
show a 
very 
feeble 
dichro. 
ism. 
Crystals in 
limestone, 
often very rich 
in inclusions 
With 
calcite, 
actinolite 
and mica. 
Very 
rich, pai- 
ticles of 
carbon, 
quartz 
grains, «& 
plates of 
musco- 
vite, ir- 
regularly 
distribf’d 
Fibrous 
decompo- 
sition 
with for- 
mation of 
calcite in 
the 
crevices. 
As contact 
mineral in 
metamorphic 
limestone, 
very rare. 
Easily distingui.shed 
from andalusite, op- 
tically, and from 
chiastolite by its 
structure. 
Rectangular 
longitudinal 
sections show 
striations and 
hbrous struc- 
ture parallel to 
the shorter 
side (i. e. axis 
c); these are 
very fine spin- 
dle-shaped 
cavities which 
appear as min- 
ute circles 
when cut at 
right angles to 
the axis c, (so- 
called ‘‘spile 
structure”) 
Coalesced 
with leucite 
or pentrating 
it. 
With 
1 nephe- 
line, 
leucite, 
! augite 
and 
olivine. 
1 
i 
The 
fibrous 
structure 
is due to 
change 
into 
zeolitic 
substan- 
ces. 
As primary 
ingredient of 
the nepheline 
-and leucite- 
basalts re- 
placing neph- 
eline, often 
very abun- 
dant. 
Easily recognized 
by the crystal lorm 
and fibrous structure. 
Easily confused with 
nepheline if color- 
less, but does not 
show hexagonal iso- 
tropous sections. Of- 
ten only disting- 
uished from serpen- 
tine by the light yel- 
low color and the 
absence of remains 
of olivine. Erom bi- 
otite distinguished 
by the lighter color 
and absence of 
strongly dichroic 
longitudinal sections. 
Poor. 
! 
