b. Double refraction 
Name. 
Chemical 
Comp, and 
reactions 
Specif. 
Gravity. 
Cleav- 
age. 
Usual Combina- 
tions and form of 
the Sections. 
Char, and 
Amt. of dbl. 
refraction. 
Colors of 
Polarization 
Color and 
Amount of 
refraction. 
I . Cal - 
cite. 
Ca CO3 . 
soluble with 
effervescence 
with H Cl. In 
acetic acid 
soluble. 
2. 6-2. 8 
(2.72) 
Incom- 
plete. 
R. 
Only in irregu- 
lar grains and 
crystal aggre- 
gates. 
Polysynthetic 
twin marking 
in- >4 R . 
i 
Very con 
siderable, 
negative. 
Generally 
not intense, 
gray, but 
brilliantly 
irridescent 
like tale 
epecially 
when in 
small grains. 
Colorless, 
white to 
gray. 
1-6543 
£= I ••4833 
( Absorb- 
tion 
feeble.) 
2. Dolo- 
mite . 
(Ca Mg) CO, 
I^ess easily 
soluble. 
2.85- 
2.95 
As 
above. 
Grains and R. 
As above. 
As above. 
3. Mag- 
nesite. 
Mg CO3 . 
still less 
soluble. 
2.9-3. 1 
As 
above. 
As above. 
As above. 
As above. 
4. Side- 
rite. 
Fe CO, easily 
soluble with 
effervescence. 
3 - 7 - 3- 9 
As 
above. 
As above. 
As above. 
Yellowish 
brown. 
5. Nepli 
elincG' p. 
a. Elae- 
olite. 
fNa K)2 (Al,) 
Si2 Og Soluble 
easily in 11 Cl 
2.65 
(2.591) 
Incom 
plete 
large 
fissures 
Only in large 
grains. 
Double 
Chiefly 
bluish green 
not brilliant. 
Green, 
reddish 
brown, 
oily lustre 
in sections 
colorless. 
b. Neph- 
eline. 
with separa- 
tion of gela- 
tinous silica, 
on evaporat'n 
cubes of salt. 
(2.58- 
2.65) 
Incom- 
plete. 
0 andl 
Hexagonal and 
rectagonal ! In 
minute crystals 
I . 0 short CO 
lumnar and 
minute irregu- 
lar grains. 
refraction 
feeble. 
Similar to 
fieldspar 
strips in very 
thin sections 
Colorless, 
trans- 
parent 
0=1.539- 
1.542 
e= 1.534 
I- 537 - 
c. Can- 
crinite. 
Soluble with 
effervescence 
separating 
gelatinous 
silica. 
2.448 
-2.454 
Incom- 
plete 
I 
Large irregular 
grains. 
Rather 
'brilliant. 
Aggregate 
polarization 
Citron 
yellow, al- 
most 
colorless 
insections. 
d. Lieb- 
enerite. 
Incompletely 
dissolved by 
H Cl. 
2.799 
-2.814 
Very 
Incom- 
plete I. 
Very dis- 
tinct aggre 
gate polar- 
zation. 
Oil green, 
in sections 
colorle.ss, 
white. 
Nepheline differs from apatite in its incomplete cleavage, microchemical reactions and 
crystal form, since apatite often exhibits, besides I and O, the plane i, and occurs in long 
columns Quartz never occurs in so minute crystals. Feldspar bands are long and twinned. 
Melilite has no hexagonal sections. 
