142, i PHYSICAL GEOGRAPHY.

 

copper, tin, lead, zinc, mercury, nickel, antimony
and aluminium. Gold, silver and platinum are
sometimes called the precious metals.

Metals occur either in the pure or native state
or condition, uncombined with other substances ;
in combination with other metals as alloys; or
in combination with non-metallic substances as
ores, such as oxides, sulphides, chlorides, carbon-
ates, etc.

Gold, silver, platinum and copper frequently
occur in the native or metallic state or alloyed
with other metals.

873. Gold, the most valuable of the metals,
does not readily rust or tarnish on exposure to
air, and is extensively employed for coinage and
jewelry. It occurs most extensively in the
native or metallic state in small granules or
irregular masses, called nuggets; in veins in quartz
rocks; in the sand or gravel of river beds; or in
alluvial deposits called placers. Native gold is
found usually slightly alloyed with other metals.

The deposits in the western parts of the United States
are the richest in the world. Those of Australia, are,
perhaps, next in importance. Mexico, Central America,
South America, Alaska, Western and Southern Africa,
New Zealand and portions of the regions adjoining the
Ural Mountains, have also rich deposits.

Perfectly pure gold is too soft to be employed for coins
or jewelry. In order to render it sufficiently hard for use
it is usually alloyed with silver or copper.

374. Silver and Platinum.—Silver, like gold, is
largely employed for coinage and for jewelry. It
does not easily oxidize, but readily blackens on
exposure to gases containing sulphur. Silver isa
widely-distributed metal. It occurs sometimes in
the native or pure state, but is usually either
mixed or alloyed with other metals, or occurs as
a sulphide. It is frequently associated with de-
posits of copper, lead and other metals.

The richest silver deposits in the United States are
situated in the western parts, especially in Colorado and
Nevada. Mexico and South America also have valuable
deposits.

Platinum, one of the heaviest metals known,
occurs native and alloyed with other metals. It
resembles silver in color. It is extensively em-
ployed for the leading-in wires of incandescent
electric lamps. Its exceedingly high melting
point renders it especially fitted for use in the
construction of small vessels, such as crucibles, or
retorts, that are required to resist exposure to high
temperatures. The principal deposits of platinum

are in the region of the Ural Mountains.

 

 

 

 

375. Iron, Copper, Tin, Lead, Zinc, Mercury,
Nickel and Antimony.—These valuable metallic
substances, with the exception of tin, are very

‘generally distributed and rich deposits occur in

all the continents.

Iron occurs in vast deposits in nearly all parts
of the world. Iron possesses a number of prop-
erties which render it by far the most useful of
all the metals. Pure or wrought iron, when
softened by heat, can readily be rolled into sheets
or forged into any desired state. It may readily
be drawn into wire. Its great tenacity renders it
extremely valuable as a building material. When
mixed with a small quantity of carbon, iron
readily fuses and it may then be cast into any
desired shape. Combined with a small quantity
of carbon it forms the well-known substance, steel.

Copper, so extensively employed in the electri-
cal industries, possesses properties that give ita
prominent place among the useful metals. It is
malleable and ductile; 7. ¢., may readily be beaten
or rolled out into sheets, or drawn out into wires.
It forms a number of valuable alloys ;—such as
brass with zinc; and gun-metal and bronze, with
tin.

The deposits of native copper in the Lake Superior dis-
tricts, in the United States, are the richest in the world.

Zine and Lead are valuable metals. Zinc is
readily rolled into sheets, and is not readily oxid-
ized or rusted. Galvanized iron, or iron covered
with a layer of metallic zine, resists oxidation.
Lead is employed for water-piping, the lining of
tanks, bullets, ete. It forms valuable alloys, and
is largely employed in the production of paints.

The most extensive deposits of lead in the United States
occur in Colorado. Zinc is found in Missouri and adjoin-
ing States.

Tin is the well-known metal employed in tin-
ware. Tin-plate consists of sheets of iron covered
with a thin layer of tin.

The principal ore of tin is the oxide. Valuable deposits
occur in Cornwall, England; in the Island of Banca; in
Australia; and in Mexico. :

Mercury is distinguished from the ordinary
metals by being liquid at ordinary temperatures.
It is extensively employed in thermometers and
barometers. Its power of forming alloys with gold
and silver is utilized in the amalgamating process
of extraction. An amalgam of mercury and tin
is employed for the reflecting surfaces of mirrors.

Valuable deposits of cinnabar, the red sulphide of mer-
cury, occur at Almaden in Spain; in California; and in
Asia Minor.