Rocks
are
classified
by
crystal
____________________
and
by
____________________
content
.
Light
coloured
,
high
-
silicon
minerals
called
____________________
form
from
____________________
viscous
magma
.
Darker
coloured
,
lower
silicon
,
higher
iron
and
magnesium
minerals
called
____________________
form
from
____________________
viscous
magma
.
Molten
material
is
liquid
or
partially
____________________
rock
.
Molten
material
found
below
the
____________________
of
the
Earth
is
called
____________________
;
____________________
the
surface
is
called
____________________
.
____________________
crystals
form
in
rock
,
which
cools
slowly
underground
;
these
include
____________________
,
gabbro
and
peridotite
.
____________________
,
dykes
and
____________________
are
rock
formations
that
are
created
when
____________________
cools
underground
.
Cooling
on
the
surface
is
rapid
and
results
in
the
____________________
crystals
of
____________________
,
rhyolite
and
andesite
.
Lava
____________________
move
over
ground
____________________
,
which
is
____________________
off
with
other
gases
leaving
the
aerated
textures
of
____________________
,
scoria
or
vesicular
basalt
.
Fragmented
bits
of
rock
and
ash
can
fuse
together
while
cooling
to
form
tuff
.
Other
surface
igneous
-
rock
formations
include
____________________
and
lava
____________________
.
