Gold and silver have long been esteemed as the king and queen of
metals, for good reason. No other members of the mineral family
surpass these two metals in nobility.
A noble metal is one that is doesn’t oxidize or corrode easily. Gold
is the most noble of all metals. It is resistant to air, water,
salt, and most acids. Heat does not destroy gold, allowing it to be
melted and remelted. Nearly all the gold ever mined is still in
existence today, in one form or another. Silver is second only to
gold in its nobility.
Metal that can be hammered into thin sheets without crumbling or
breaking is called malleable. Ductile metals may be stretched under
pressure into thin wires without breaking. Gold is the most
malleable and ductile of all metals, silver the second. Gold can be
pounded into sheets less than four millionths of an inch thick. An
ounce of gold can be drawn into a wire more than 40 miles long.
Malleable and ductile metals are soft and easy to work with. Gold
and silver in their pure states, however, are too soft for making
objects that will last. Therefore, other metals are frequently
combined (alloyed) with both gold and silver to make them harder.
Silver alloys usually retain their silver color. The color of gold
varies with the kind and amount of other metals combined with it.
Red golds contain silver, copper, and zinc. Rose gold contains no
zinc. Yellow golds contain more silver and less copper than red
golds. Green golds may contain cadmium and zinc. Adding iron to an
alloy produces blue gold.
White gold was formerly an alloy of gold and silver, which
tarnished. White gold today is usually a gold and nickel alloy. It
may also contain palladium, manganese, or tin, and does not tarnish.
Nu-gold, Merlin’s Gold, and jewelers’ bronze are alloys of copper
and zinc. They contain no gold.
Fineness is a measure of the purity of gold or silver. Fineness in
gold is usually specified by a karat rating; in silver, it is
expressed as a percentage.
Karats are based on the number 24. The rating is a fraction, with 24
always as the denominator (bottom number). The amount of gold is the
numerator (top number). Pure gold is 24/24th gold. We traditionally
drop the bottom number, so that pure gold, or 100% gold, is called
24 karat gold.
Gold that is 18 karat is a gold alloy containing 18 parts of gold to
six parts of other metal. Fourteen karat gold, which is 14 parts
gold and 10 parts other metal, is the most popular gold in the U.S.
Alloys containing less than 10 karats of gold cannot be legally sold
as gold in the U.S.
The term solid gold does not mean pure gold. Solid gold means only
that the item is not hollow. The karat rating tells how much gold is
in the object. Gold-filled means a layer of gold has been fused to
another metal. Again, the karat rating tells how much gold the item
contains. For example, 14K GF means a layer of 14 karat gold has
been bonded to another metal. The item itself is not made completely
from 14 karat gold. Rolled gold is essentially the same as filled
gold, except that the layer of gold alloy is thinner.
Gold electroplate means that a coating of gold alloy has been
deposited on another metal by electrolysis. The layer of gold alloy
must be at least seven millionths of an inch (or 175 microns) thick.
If the layer is thinner, it must be called it gold wash or gold
flash. A layer of gold alloy more than 10 millionths of an inch
thick may be called heavy gold electroplate.
The weight of gold alloy in objects is often expressed as a
fraction. Thus, describing something as one-tenth (1/10) 14K means
that one-tenth (or 10%) of the total weight is 14 karat gold. It
does not mean that the object is 1/10 gold.
Sterling silver is an alloy containing 92.5 parts silver and 7.5
parts other metal. It is also called 92.5 percent silver or 925
fineness. Although copper is the standard metal used in sterling
silver, other metals may be used.
Jewelry silver, used more in Europe than it is in the United States,
is often 800 fineness, which means that it is an alloy of 80 percent
silver and 20 percent other metal, usually copper.
Spring silver is Sterling silver that is hardened to give it the
"spring" needed for items such as money clips. Coin silver is an
alloy of varying amounts of silver and copper. Sheffield plate is
two thin sheets of silver with a sheet of copper fused between them.
German silver, or nickel silver, contains no silver. It is an alloy
of copper, nickel and zinc. German silver is also known as white
copper.
Silver is well known for its tarnish. Tarnish is a dark layer built
up on the surface of silver, resulting from contact with sulfur
compounds in the air. Some body chemicals may also cause tarnish. It
does not destroy the underlying silver and may be polished off
(although sometimes not easily!).
When gold darkens skin, it is usually due to body salts interacting
with the copper or silver in a gold alloy. Smog can also cause a
tarnish on some gold alloys that will rub off on the skin.
Early civilizations associated gold with the sun and considered it
masculine. They regarded silver as feminine and linked it with the
moon. Gold has been long prized as a symbol of life and immortality.
The whiteness of silver symbolizes purity for many.
****Sandra I. Smith, Writer ****