Phlogopite or A
magnesium mica of a yellowish-brown to brown-"Amber Mica" ish-red
color. It often exhibits asterisms in transmitted light due to
inclusions. This mineral is used as an insulator in electrical
appliances. Most of the mica used in this country is imported from
Canada.
Pitchblende; Oxide of Uranium. (See Uraninite.) Experiments
with pitchblende led to the discovery of the element,
Radium, which in the form of a chloride, attracted
the attention of the whole scientific world. This pitchblende was
obtained from the mines at Joachimsthal, Bohemia. (See Radium.)
Platinum; This most valuable of all metals was discovered in the
mines of Choco, Peru, in 1741. It occurs in the metallic
state in the form of rounded or flattened grains
of a metallic luster and white color, and is the heaviest of known
metals. It is exceedingly ductile and malleable and does not tarnish
Platinum
is found in the sands of rivers or beaches, in placer deposits in
flattened scales or small grains. Nuggets of considerable size are
sometimes found, the largest known weighing about 18-3/4 kilos. It
occurs in the Ural Mountains, in South America, the Pacific States and
at Good Springs, Nev.
On
account of its infusibility and its power to resist corrosion. Platinum
is used extensively for crucibles and other apparatus of the chemist.
It is also used by dentists and in the manufacture of surgical
instruments. The most important use of this metal in the industries, is
in the manufacture of sulphuric acid.
Platinum is also used most extensively in the manufacture of watches, rings, bracelets, chains, and all varieties of jewelry.
Plattnerite: Lead
Dioxide. Oxygen 13.4%, Lead 86.6%. Occurs usually massive; rarely in
crystals; sometimes granular and in crusts. Color iron-black, streak
chestnut-brown. Translucent to nearly opaque. This mineral is found at
Leadhills and at Wanlockhead, Scotland, and at the "As You Like It"
mine in Idaho. Named after the Mineralogist, K. F. Plattner.
Polianite: Manganese
Dioxide. Oxygen 37%, Manganese 63%. Occurs in composite parallel
groupings of minute crystals; also forms outer shell of crystals
having the form of Manganite. This mineral is extremely rare, being
found in measure-able crystals only in Bohemia.
