even in thinest sections. 
TABLE 1. 
Color and 
. histi'c. 
Structure. 
Association. 
Alterations. 
Occuri'ence, etc. ! 
Iron black, 
b 1 u e-b lack 
metallic lustre 
Often in 
beautiful cru- 
ciate aggre- 
gates, or, as 
result of alte 
ration, about 
a mineral or 
in its cleavage 
lines. 
With nearly 
all rock -form- 
ing minerals, 
parti cularly 
a u g i t e , oli- 
vine, plagio- 
close, nephe- 
lin. and leu- 
cite. 
Very often 
into limonite, 
forming a red- 
ish brown 
band about 
the crystal of 
magnetite. 
1. As primary ne- 
cessary component of 
basic eruptive rocks 
and accessory in near- 
ly all crystallines. 
2 . As result of al- 
teration of olivine, 
augite, hornblende 
and biotite. 
- 
Into titanite 
a n cl limonite 
(Forms the 
transition t o 
titanic iron.) 
Pi imary, in basalts 
and crystalline slates. 
In reflected 
light yellow, 
metallic lustre 
Into limon- 
nite. 
Rarely as accessory 
secondary component 
of altered basic erup- 
tives and (also pri- 
mary) in crystalline 
slates. • 
1 
Blackish 
brown, metal- 
lic lustre. If 
altered, gray 
in reflected 
light. 
With plagi- 
oclase, augite, 
horn blende, 
and olivine. 
Into titanite 
and rutile with 
specular iron. 
In basic eruptives, 
(particularly granu- 
lar diabases, gabbros, 
basalt, pikrit) ; also 
in crystalline slates. 
[Distinguished from 
magnetite by form of 
sections and altera- 
tions.] 
Iron black 
with metallic 
lustre. 
Rarely in cryst. 
slates, clay- and clay- 
mica-slates, gneiss, 
limestone; and as in- 
clusions in staurolite, 
andalusite, chiasto- 
lite, dipyre, etc. 
Bronze yel 
low. Metallic 
lustre. 
i 
i 
Very rare in cryst- 
alline slates and con- 
tact slates 
Ea.sily distinguished 
from pyrite in re- 
flected light by the 
lustre. 
' 
