All That Glitters
"Gold! gold! gold! gold! Bright and yellow,
hard and cold".
Thomas Hood (1799-1845)
In his play, 'The Merchant of Venice',
Shakespeare writes, "All that glitters is not
gold; often have you heard that told", and with
respect to jewellery, he's right on the money.
While gold remains the pre-eminent jewellery
metal, there are numerous other choices
available, such as brass, copper, palladium,
platinum, silver, stainless steel, titanium, and
tungsten. While this can make shopping for
jewellery potentially confusing, the following
pages guide you through the three most popular
jewellery metals: gold, silver and platinum.
One common jewellery question is, "What is a
troy ounce?" Gold, silver, platinum, and other
precious metals are traditionally weighed and
traded in troy ounces. Weighing 31.10 grammes, a
troy ounce is about 10 percent heavier than the
avoirdupois ounce used in cooking. Nowadays,
metric units are also used to weigh precious
metals, but there are no signs of the metric
system replacing the troy ounce in the near
future. As an Englishman once told me, "We are
going metric - inch by inch".
Gold
Still remembering the periodic table from my
university days, gold's atomic number is 79 and
its chemical symbol is 'Au', from the Latin name
for gold, 'aurum'. Our modern word for this
metal is derived from the Old English for
yellow, 'geolo'. As a rare metallic element of
high economic value, gold has long been regarded
as the most precious of precious metals.
While some sources date its discovery to circa
3000 BC, it is possible that the first gold
nuggets were mined in the Transylvanian Alps as
early as 6000 BC! Since then, it has become a
potent symbol of wealth and social status. For
thousands of years, gold has been valued as a
global currency, a commodity, an investment and
an object of beauty. Bestowed upon people and
used in worship, gold has forged civilisations
and inspired legends. Gold's rich lustre and
unique texture assures its place in jewellery,
yet as a hard global currency, gold's economic
importance is unquestioned.
Gold is a precious metal with intrinsic value.
From dinky pawnshops to the venerable London
Gold Exchange, enormous amounts of gold changes
hands every day. Gold pricing is always based on
its purity and weight. While gold reserves
stopped being the basis of world monetary
systems in the early nineteen-hundreds, a large
proportion of the world's gold continues to be
held in government reserves. Today, gold is used
as an effective hedge against fluctuations in
the United States Dollar (USD), the world's main
trading currency.
Gold is mined from the crust of the earth and
copper ores, and its leading world producer is
South Africa. Since the break-up of the former
Soviet Union in 1991, the U.S.A. has become the
second largest gold-producing nation, followed
by Australia, Canada, China, Russia, Peru and
Indonesia.
Amazingly strong, gold is also the most
malleable of all precious metals. Forever
glimmering and glittering, pure gold never
tarnishes or corrodes. Even though about 75
percent of
the gold produced goes into jewellery and watch
production, pure gold is too soft for most
ornamental applications. This objectionable
inclination of pure gold has resulted in it
being alloyed with other metals to improve its
durability. The international measure of gold
fineness or purity is 'karat', which is
typically abbreviated 'K'. This should not be
confused with 'carat' which is a unit of weight
in gemstones (click
here for more). The gold
content of any object is expressed as a ratio of
24 parts. While pure gold is 24K, the gold
purities typically seen in jewellery are:
- 22K: 91.6 percent pure gold (22 parts gold and 2 parts alloy)
- 18K: 75 percent pure gold (18 parts gold and 6 parts alloy)
- 14K: 58.5 percent pure gold (14 parts gold and 10 parts alloy)
- 10K: 41.7 percent pure gold (10 parts gold and 14 parts alloy)
- 9K: 37.5 percent pure gold (9 parts gold and 15 parts alloy)
|
 |
| |
White Gold
|
| |
 |
| |
Rose Gold
|
| |
 |
| |
This photograph illustrates how gold
preferences vary from country to
country. The Thai wedding ring on
the left is 24K Yellow Gold while
the Russian wedding ring on the
right is 18K Rose Gold |
Gold's different colours are produced by simply
varying the alloy metals. The three most popular
colours are yellow, white and rose.
-
Yellow Gold:
Alloyed with silver and copper to
display its timeless colour, yellow is gold's
most common colour.
- White Gold: A popular modern alternative to
yellow gold, white gold is created by bleaching
pure yellow gold white. While 9K, 10K and 14K
white gold is bleached white using silver,
because of its higher purity (75 percent), 18K gold
requires a stronger bleaching agent, such as
palladium (Pd), a precious platinum group metal.
Though nickel (Ni) can be used to alloy 18K
white gold, this should be avoided as its
release can cause allergic reactions. Providing
a hard, shiny, unmatched finish, rhodium (Rh)
electroplating has become the international
industry standard for nickel-free white gold
alloys. Rhodium was discovered by William
Wollaston in 1803. Approximately three times
more expensive than platinum, rhodium is the
most expensive platinum group precious metal.
-
Rose Gold:
Rose gold, also known as pink gold or
Russian gold (this gold colour has been popular
in Russia since the beginning of the 19th
century), is alloyed with copper. Typically a
striking pinkish rose colour, the higher the
copper content, the stronger the red colouration.
Interestingly, pink gold is increasingly used in
men's horology (very expensive watches).
Apart from gold colours, there are other gold
jewellery applications you should be aware of:
- Gold filled, also known as gold overlay, is a
gold layer bonded to a support metal that
constitutes 5-10 percent of the total weight of
the item.
- Rolled gold plate is a variety of gold filled,
where the gold layer bonded to a support metal
is less than 5 percent of the total weight of
the item.
-
Gold plated is a thin plating of gold bonded to
the support metal. Items that are gold plated
contain less gold than those that are gold
filled.
- Electroplating, also known as gold flashed or
gold washed, is an electrical process that
affixes gold, a gold alloy or another precious
metal to a support metal with a minimum
thickness of 0.175 microns. Heavy gold
electroplating is when the minimum thickness is
2.5 microns. Items made entirely of gold can be
electroplated (e.g. the rhodium electroplating
of white gold).
- Vermeil, pronounced 'ver-may', is typically
sterling silver covered with a layer of gold
plate. Deriving its name from the French word
for 'veneer', the original fire-guilding vermeil
process developed in 18th century France has
been replaced by electrolysis. Also known as onlay, double or silver gilt, in vermeil the
gold must also be at least 10K and have a
minimum thickness of 1.5 microns.
- Gold leaf is ultra thin pounded gold. Pure gold
leaf has a long tradition in European cuisine,
where exotic dishes are given the ultimate
edible presentation.
Silver
|
 |
| |
925 Sterling Silver |
Mined from ores such as argentite, silver's
history dates back more than 5,000 years. A
popular and affordable choice for jewellery,
silver has been used by virtually every
civilisation. Silver is also used to craft
'objets d'art', such as silverware (no surprise
there) and hollowware (tableware, such as bowls,
pitchers, teapots and trays that serve as
containers or receptacles). The chemical symbol
for silver 'Ag' is derived from the Latin word
for silver, 'argentum'. Our modern name for
silver comes from the Old English word 'seolfor'.
Relatively malleable, pure silver is softer than
gold or platinum. As with gold, silver is
typically alloyed with secondary metals such as
copper for strength. Similar to platinum, silver
purities are expressed as parts per thousand.
'Sterling' or '925' silver is 92.5 percent pure
and the standard for high-quality silver
jewellery. For every 1,000 parts in sterling
silver, 75 of them (7.5 percent) is an alloy.
Another commonly seen silver purity is
'Britannia' or '958' silver, which is 95.8
percent pure.
Platinum
Gold might be regarded as the most precious of
metals, but did you know that platinum (Pt) is
60 times rarer? Platinum is also purer, stronger
and denser than gold. A natural white metal,
platinum's durability makes it extremely
wearable. Platinum is also hypoallergenic,
meaning it has a decreased tendency to provoke
an allergic reaction. Discovered in 1735 by
Julius Scaliger, platinum is derived from the
Spanish 'platina', which means 'little silver'.
While only 'officially' discovered in the 18th
century, it has appeared throughout history, but
not always as a unique metal. Platinum's Spanish
name is likely in reference to sightings by
conquistadors, who thought its small silver-coloured
nuggets were undeveloped silver that had not
fully matured.
While it's tempting to think of platinum as a
relatively new jewellery metal, this is actually
incorrect. Platinum was a big hit with the Sun
King, France's Louis XIV, who declared it to be
the only metal fit for kings. From the turn of
the 20th century until 1940, platinum was
actually the preferred precious metal for U.S.
manufactured jewellery. Declared a strategic
metal during WWII, platinum never regained its
previous popularity.
Platinum purity is measured in parts per
thousand. The most common platinum purities are
950 (95 percent pure platinum), 900 (90 percent
pure platinum) and 850 (85 percent pure
platinum). |
