rax bead gives usual indications of
iron.

~Magnetite~, Fe_{3}O_{4}, FeO . 31, Fe_{2}O_{3} . 69.--

H = 5.5-6.5, G = 5.17-5.18.

Color, iron-black. Lustre, shining and metallic. Pulverized, its powder
is black. It is strongly magnetic. Fuses with difficulty before the Bp.
on Ch. In borax bead reacts for iron.

~Pyrites~, FeS_{2}, Fe . 47, S . 53.--

H = 6.0-6.5, G = 4.95-5.20.

Color, brass-yellow. Lustre, metallic. Occurs commonly in cubes. It
often contains small quantities of Au, Ag, Cu, As, Co, and Mn. Heated in
an ignition tube gives a sublimate of sulphur, the residue becoming
magnetic. Before the Bp. on Ch. in O. F. sulphur is burned off and the
red oxide remains. This residue may then be examined for iron, etc.

~Marcasite~ (White Iron Pyrites).--Having the same general composition as
pyrite, but much lighter in color. Crystals, prismatic. Before the Bp.
on Ch. behaves like pyrite.

~Pyrrhotite~, Fe_{7}S_{8}, Fe . 60.5, S . 39.5.--

H = 3.5-4.5, G = 4.58-4.64.

Color, bronze-yellow. Closely resembles pyrite, but may be distinguished
from it by being feebly magnetic. Heated in an ignition tube yields no
sublimate. Before the Bp. on Ch. fuses to a magnetic globule, which
exhibits a yellowish crystalline structure when fractured.

~Mispickel~, FeAsS, Fe . 34, As . 46, S . 20.--H = 5.5-6.0, G = 6.0-6.2.
Color, silver-white. Lustre, metallic; very brittle. Often associated
with it we find small quantities of Co, Ag, and Au. Heated in an
ignition tube it first yields a red sublimate of sulphide of arsenic,
and then afterward a crystalline sublimate of metallic arsenic. Before
the Bp. on Ch. emits dense fumes of arsenic and deposits a coating on
the coal; it then fuses to a globule which behaves like pyrrhotite.

~Siderite~, FeCO_{3}, FeO . 62, CO_{2} . 38.--H = 3.5-4.5, G = 3.7-3.9.
Color, grayish yellow to reddish brown. Lustre, pearly. Crystallizes in
rhombohedrons with curved faces; these crystals are distinctly cleavable
and massive. Heated in an ignition tube it decrepitates with evolution
of carbon dioxide. Before the Bp. on Ch. infusible. Before the Bp. on
Ch. with Na_{2}CO_{3} it fuses to a magnetic mass. With borax bead it
reacts for iron and sometimes for manganese.

ORES OF LEAD

~Galena~, PbS, Pb . 87, S . 13.--

H = 2.5, G = 7.4-7.6.

Color, bluish gray, slowly tarnishing. Lustre, metallic. Crystals in the
form of cubes. Heated in an ignition tube it somet