A. Can be scratched by a fingernail
Cerargyrite Shiny white or Appears waxy; 1-1½
gray knife cuts it
smoothly; turns
violet brown to
black when
exposed to light
Gypsum White Transparent 2
selenite variety
commonly occurs
as flat,
diamond-shaped
crystals; splits
into thin, flat
sheets that will
not bend without
breaking
Muscovite (white White Splits into thin, 2-2½
mica) flat, transparent
sheets that will
bend without
breaking
B. Cannot be scratched by a fingernail but can be scratched by a copper
penny
Barite White Rather heavy; 3-3½
cleavage
fragments may be
flat and slab-like
Calcite White Dilute 3
hydrochloric acid
fizzes on
calcite; perfect
cleavage in 3
directions gives
rhomb-shaped
fragments
Celestite White Not quite as 3-3½
heavy as barite;
crystals commonly
prism-shaped or
flat-looking;
some cleavage
fragments are
flat and slab-like
Halite White Salty taste; 2½
dissolves in
water;
cube-shaped
cleavage fragments
Muscovite (white White Splits into thin, 2-2½
mica) flat, transparent
sheets that will
bend without
breaking
C. Cannot be scratched by a copper penny but can be scratched by an
ordinary pocket knife
Barite White Rather heavy; 3-3½
cleavage
fragments may be
flat and slab-like
Celestite White Not quite as 3-3½
heavy as barite;
crystals commonly
prism-shaped or
flat-looking;
some cleavage
fragments are
flat and slab-like
Dolomite White Commonly occurs 3½-4
as granular
masses and as
rhomb-shaped
crystals; dilute
hydrochloric acid
may fizz slightly
on dolomite
Fluorite White Cleavage in 4 4
directions can
give fragments
that are shaped
like octahedrons;
crystals commonly
cubes
Opal White Curved, 5-6
conchoidal
fracture;
transparent
_hyalite_ variety
resembles ice
D. Cannot be scratched by an ordinary pocket knife but can be scratched
by quartz
Opal White Curved, 5-6
conchoidal
fracture;
transparent
_hyalite_ variety
resembles ice
Quartz White Curved, 7
conchoidal
fracture; _rock
crystal_ quartz
commonly 6-sided
prism with
pyramid-like ends
E. Cannot be scratched by quartz
Topaz White Perfect basal 8
cleavage gives
flat, plate-like
fragments; notice
hardness