A. Will leave mark on paper
Argentite Shiny, blackish Lead-gray color 2-2½
to lead grey that tarnishes to
dull black; knife
cuts it smoothly;
heavy; may occur
as masses and
coatings
Graphite Black Greasy feel; very 1-2
soft; splits into
thin flakes
Pyrolusite Black Very soft; will 1-2
soil fingers; may
be powdery
B. Does not readily leave mark on paper but can be scratched by an
ordinary pocket knife
Chalcocite Grayish black Shiny lead-gray 2½-3
color that
tarnishes to dull
black; knife cuts
it smoothly; may
have a black
sooty coating;
commonly occurs
as compact or
granular masses
Hollandite Black May occur as 4-6
rounded masses
Limonite Rusty, yellowish Some specimens 5-5½
brown have shiny black
surface; notice
streak
C. Cannot be scratched by an ordinary pocket knife
Braunite Steel gray or Luster is 6-6½
black submetallic
Cassiterite Pale brown, pale Submetallic 6-7
yellow, or white luster; heavy;
notice streak
Hematite Dark reddish brown Notice streak; 5½-6½
commonly occurs (may be
as granular or softer)
compact masses
Hollandite Black May occur as 4-6
rounded masses
Limonite Rusty yellowish Some specimens 5-5½
brown have shiny black
surface; notice
streak
Magnetite Black Fragments cling 6
to a magnet
Pitchblende Brownish black Brownish black, 5½
greenish black,
or black;
radioactive;
heavy; may appear
dull or greasy