-
Because obsidian is
metastable at the Earth's
surface (over time the gl****
devitrifies,
becoming fine-grained
mineral crystals),
obsidian older than Miocene...
- one face may be
exposed to
conditions causing the
fibers to
partially devitrify.
Depending on the
chemical composition of the gl****y
fiber and the time...
-
temperature just
insufficient to
cause fusion. In this way, the crystalline,
devitrified material,
known as Réaumur's gl****
porcelain is produced.
Although generally...
- they are
surrounded by a gl****y or
felsitic base. When
obsidians are
devitrified, the
spherulites are
often traceable,
though they may be more or less...
- due to the
effect of
pressure and temperature. The
pyroclastic flows devitrify and weld
together and
spread during the
volcanic action,
forming a kind...
- and the gl**** plies. A
sacrificial outer layer that
cracks rather than
devitrifies is the
first failsafe.
Circular bullseyes,
linear cracks,
crack chips...
-
bentonite is more common. In
stratigraphy and tephrochronology,
completely devitrified (weathered
volcanic gl****) ash-fall beds are
sometimes also referred...
- glaze.
Developed in
Holland to
imitate Chinese blue and
white porcelain.
Devitrify When a
glaze recrystallise during the
cooling stage of firing. Results...
-
absorb wavelengths of
energy differently.
Since fluorite gl****es tend to
devitrify very readily, it can be
difficult to
avoid crystallization during processing...
-
pigments that were
originally blue are now green: the blue frit can "
devitrify" so that the "copper
wollastonite predominates over the
lesser component...
