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About Gold & Gold Glossary |
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Gold is the most malleable and
ductile metal; a single gram can be beaten into a sheet of one square meter,
or an ounce into 300 square feet. Gold leaf can be beaten thin enough to
become translucent. The transmitted light appears greenish blue, because
gold strongly reflects yellow and red. Gold readily forms alloys with many
other metals. These alloys can be produced to increase the hardness or to
create exotic colors (see below). Native gold contains usually eight to ten
percent silver, but often much more — alloys with a silver content over 20%
are called electrum. As the amount of silver increases, the color becomes
whiter and the specific gravity becomes lower.
Gold is a good conductor of heat and electricity, and is not affected by air
and most reagents. Heat, moisture, oxygen, and most corrosive agents have
very little chemical effect on gold, making it well-suited for use in coins
and jewelry; conversely, halogens will chemically alter gold, and aqua regia
dissolves it via formation of the chloraurate ion.
Common oxidation states of gold include +1 (gold(I) or aurous compounds) and
+3 (gold(III) or auric compounds). Gold ions in solution are readily reduced
and precipitated out as gold metal by adding any other metal as the reducing
agent. The added metal is oxidized and dissolves allowing the gold to be
displaced from solution and be recovered as a solid precipitate.
Recent research undertaken by Sir Frank Reith of the Australian National
University shows that microbes play an important role in forming gold
deposits, transporting and precipitating gold to form grains and nuggets
that collect in alluvial deposits.
High quality pure metallic gold is tasteless, in keeping with its resistance
to corrosion (it is metal ions which confer taste to metals).
In addition, gold is very dense, a cubic meter weighing 19300 kg. By
comparison, the density of lead is 11340 kg/m³, and the densest element,
Iridium, is 22650 kg/m³.
For more
information about Pre-columbian Gold » |
For
more up to date information about mining gold in Central America: Gold
Mining and Exploration in Central America [PDF]
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How They Made It
The story of early Peruvian gold
mining & production |
Mining and extracting the ore |
Mining tool used to extract copper |
Ore |
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Grinding the ore in preparation for smelting
A grinding stone for crush the ore
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An adobe smelting oven
Transporting gold ore & refined metals by llamas |
Prills of metal after the smelting process
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Moche gold ingot
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An ingot of pre-columbian copper |
An ingot of pre-columbian copper |
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Ingot of pre-columbian gold |
Copper Ingots from Sitio Conte Pamana |
Gold working stone hammers & plates
Gold embossing set |
Stone template with round holds for pressing gold
Meticulously crafted design can be cut for adornments |
A laminate gold form on which gold can be formed and hammered and embossed
into shape |
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Gold Glossary |
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A mixture of two elements, at least one of which
is a metal, which form a new metal with desired properties. |
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The smallest unit of an element that retains its
properties. |
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The ability of a mineral to transmit heat,
electricity, or sound. |
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A naturally-occurring combination of two or more
elements in a specific ratio. Compounds need a chemical change to separate
into their constituent parts. |
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Gradual chemical destruction of a mineral.
Corrosion often, but not always, operates through oxidation. Tarnish is a
form of corrosion. |
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A unit of a mineral that has a symmetrical shape
with flat, angled surfaces. The shape arises from an orderly arrangement of
the mineral's atoms. Crystals can aggregate to form distinctive overall
shapes. |
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The average mass per unit volume of a substance. |
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A natural concentration of a mineral in Earth's
crust. |
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The ability of a mineral to be pulled into wire. |
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A substance that cannot be broken down into
simpler substances by chemical means. Elements are composed of a single kind
of atom. |
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A measure of the amount of pure gold in a metal,
in parts per thousand. |
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A measure of the amount of pure gold in a metal.
One karat is 1/24th of the total weight of the object. 100 percent pure gold
is 24 karats. |
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The manner in which a mineral reflects light. |
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A measure of how hard or soft a mineral is
relative to diamond, the hardest mineral on the 10-point Mohs scale of
hardness. |
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Hot water, steam, and gases trapped in fractured
or porous rocks underneath Earth's surface. |
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A mineral's ability to be hammered into thin
sheets. |
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A measure of the total amount of matter in a
body. |
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A class of elements that have characteristic
physical properties. Metals are generally good conductors, and are
reflective, malleable, and ductile. |
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A solid substance with a crystal structure that
formed via geologic processes. Minerals can be either elements or compounds. |
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A combination of two substances that can be
separated by a physical change. |
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The pure or nearly pure form of an element found
in nature. |
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 A
lump of gold found in nature. |
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Rock from which valuable minerals can be
extracted. |
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To become chemically combined with oxygen. |
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A deposit of valuable minerals in a lake, river,
or seabed. |
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Any naturally occurring combination of one or
more minerals. |
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To dull the luster of a mineral by exposure to
air or dirt. Tarnish is a form of corrosion or oxidation. |
tumbaga
Click here for more » |
Tumbaga was the name given by
Spaniards to a non-specific
alloy
of gold
and copper which they found in widespread use in
Pre-columbian Mesoamerica. |
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A mineral deposit in a fracture in the Earth. |
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The amount of space occupied by a
three-dimensional object or region of space. |
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