Natne. 
Chem. 
Comp and 
Reactions 
Specif. 
Grav. 
Cleav- 
age. 
Usual combi 
nations and 
form ofseds. 
Twins. 
Optical 
detemninants . 
Double 
refraction. 
4. Bronz- 
ite. 
m (Mg Si 
O3) 
-|- n [Fe Si 
O3] 
Insoluble. 
3 - 3-5 
(3-12-3.25) 
Com- 
plete- 
I 
and 
partial 
in i-i. 
Long col- 
umnar 
I . i-i . 
i-i prevail- 
ing. 
very similar 
to mono 
clinic augite 
Repeated 
twinning in 
giving the 
cleavage 
plates in i-i a 
wavy appear- 
ance. ‘'Knee”- 
shaped twins 
in m-i in 
stellate groups 
occur rarely in 
porphyritic 
eruptives. 
As in 
enstatite. 
Positive. 
Sections 
paralel to 0. 
& i-i sho w 
simply an 
open cross 
with traces 
of Lemnisci. 
Sections 
perpendic- 
ular to an 
optical axis 
show one 
ring or none 
5. Antho- 
phyllite. 
n Mg Si Oo 
4 -FeSi O3 
Insoluble. 
3-187- 
3-325 
i-I 
I 
i-b 
incom- 
plete. 
In foli- 
aceous 
masses rare- 
ly in crys- 
tals. Sec- 
tions as in 
monoclinic 
hornblende. 
Optical axial 
plane parallel 
i-i acute bisec- 
trix at right 
angles to 0 
c^=C 
b=h 
a=a 
Positive, 
strong. 
bb. 
Disappearance of obtuse 
1. Hyp 
ersthe 7 te. 
2 . Proto- 
basite 
and 
basite. 
(See 
below.) 
As in 
Bronzite 
but with 
more iron. 
3 - 3 - 3-4 
I 
com- 
plete 
i-i 
con- 
choidal 
frac- 
ture i-i 
incom- 
plete 
1== 
about 
92° 
Large irreg- 
ular grains 
and minute 
columns 
with the 
combinati’n 
I . i-i. i-i, 
oXsoyi-l. 2-1 
3 - 2 - 3 - 2 - 
Knee-shaped 
twins as in 
bronzite. 
Opt axis plane 
parallel i-i 
obtuse bisec- 
trix at right 
angles to O 
acutebisectrix 
at right 
angles to 
i-i 
c^=c 
b=b 
a=a 
Large axial 
angle. 
Parallel to 
0 positive, 
to i-i neg- 
ative, fee 
bier than in 
mono- clinic 
augite. 
Protohasite (diaclasite) and basite have the same composition as bronzite -f- H2 O. In 
sharply defined crystals, columnar grains and irregular scales. Cleavage i-i and 1 . Opt. axis 
plane || i-i. obtuse bisectrix at right angles to O , the acute bisectrix to i-i. Specif, grav. of 
protobasite 3 054, of basite 2. 6-2. 8; the former is is light yellow, with rather brilliant polari- 
zation. In gabbro and porph. augite-bearing plagioclase rocks, changes to basite which is 
dirty light green, and is always a product of decay of rhombic augite. 
