United
States, especially the Ohio, and the rivers of Wisconsin, Iowa and
Minnesota. The very finest Pearls are fished for and obtained from the
Bay of Bengal, at Ceylon and in the Persian Gulf.
The Pearl that is perfectly round and of fine luster is among the most precious of stones.
Pectolite:
Silicate of Lime (33.8%) and Soda (9.3%). This usually occurs in
fibrous or columnar masses. A compact tough form, green in color and
resembling Jade, is used by the Alaskan Indians for ornaments,
implements, hammers, etc. It occurs also as crystals on the walls of
rocks. It is found in Alaska, Thunder Bay region. Lake Superior, the
Alps, Greenland, and, also in clefts in trap-rock at Bergen Hill, N. J.
Pentlandite: Sulphide
of Iron and Nickel. Sulphur 36%, Iron 42%, Nickel 22%. It occurs
massive and in granular aggregates, light bronze-yellow in color. It is
mined as an ore of Nickel, at Sudbury, Ontario, and with Chalcopy-
rite in Southern Norway.
Peridot: Gem
variety of Chrysolite, which is called Peridot by the French
mineralogists, and Olivine by the German. It is yellowish olive-green
in color, and ranks as a semiprecious stone of about the same value as
Tourmaline, though far in advance in brilliancy. (See Olivine.)
Perovskite: Calcium Titanate. Titanium Oxide 59%, Lime
41%. Occurs almost exclusively in crystals, cubic in
habit with color varying from pale yellow, through
orange to reddish brown and grayish-black. It is found in the Urals,
in Switzerland, Italy, Brazil, and in Magnet Cove, Arkansas.
Petrified Wood: Petrified,
Silicified, Opalized, Jasperized or Aga-tized Wood, are various names
for the replacement of wood fibers by different minerals. The rich
warm blending colors, and the remarkable polish that this material is
susceptible of, are the main features that will always give it a high
place among minerals.
The
unique and wonderful petrified forest near Adamana, Arizona, covers
nearly 1,000 acres. The giant trees that once grew there have long
since fallen through volcanic eruptions and have become silicified.
Some entire trees with limbs and branches, are still intact. One of the
largest and finest of these trees, nearly four feet in diameter, spans
a deep gully, its ends resting on either bank, and is known as "Agate
Bridge." All the logs both great and small, are of great beauty and
variety of color. Amethyst abounds, the
