- The type of
twinning can be a
diagnostic tool in
mineral identification.
There are
three main
types of
twinning. The
first is
growth twinning which can...
-
Plagioclase almost universally shows a
characteristic polysynthetic twinning that
produces twinning striations on [010].
These striations allow plagioclase...
- tabular, prismatic,
rhombohedral crystals, m****ive or
granular Twinning Polysynthetic twinning common Cleavage None –
parting in 3
directions Fracture Conchoidal...
-
Sixlings are
common in aragonite.
Polysynthetic twins are
similar to
cyclic twins through the
presence of
repetitive twinning; however,
instead of occurring...
-
acicular to
tabular prismatic Twinning Common as
contact or
penetration twins on {100} and {201}.
Polysynthetic twinning also present.
Cleavage Perfect...
- in
extinctions viewed under cross polarization.
Ulexite displays polysynthetic twinning parallel to the elongation,
along {010} and {100} (Murdoch, 1940)...
- it as soon as a dome is cut. The
Journal of
gemmology mentions polysynthetic twinning (parallel lines). The star
effect occurs in
other sapphire colours...
-
tabular and tabular-prismatic
types are much less common.
Complex polysynthetic twinning is very
often observed.
Belomorite is of
igneous origin; it is part...
- crystals,
irregular grains, m****ive
Twinning On {101}.
Crystals shocked by
meteorite impact show
polysynthetic twins on {112}
Cleavage {110} and {111} Fracture...
-
prismatic crystals; tabular, rhombic,
flattened along [010]
Twinning Polysynthetic twinning produces a grid
pattern on [100]
Cleavage Perfect on [001]...
