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Test for Gold
Name: Joyce
Status: other
Grade: 9-12
Location: FL
Country: N/A
Date: May 2006
Question:
Is there any kind of household test to do to see
if gold is fake? I have had some gold given to me that i would
like to test. I can only find 14k stamped on some pieces, and I
cannot tell what the other pieces are stamped with.
Replies:
NOTE: The words karat and carat are not the same thing. Karat
works the idea of purity of a substance and carat is expressing
how much weight in a gemstone. One carat is 200 milligrams.
There are a couple of ways that you may use depending upon the
particular piece you have. First, however, the "karat"
value loosely indicates the gold content: 24k generally meaning
greater than 99% gold. However, the "karat" value differs from
country to country. Also the alloying metals are not the same: Ag,
Cu, Zn, Ni, Pb, and Pt are used. Alloying gold is not always meant
to make it fake.
Pure gold is very soft, and in most applications, such as jewelry
it is too soft to be used pure. A second way is to measure the
specific gravity (density). Pure gold has a density of 19.32
gm/cm^3 while 14k gold has a density between 12.9 and 14.6 gm/cm^3,
depending upon the composition of the alloy. Legend has it that
Archimedes discovered the principle of buoyancy by measuring the
difference in the density of the king's new crown using this
method. An experienced jeweler should be able to distinguish the
pieces at little or no charge. Below are some interesting websites
on gold and its alloys.
http://www.bbc.co.uk/dna/h2g2/A3327103
http://www.24carat.co.uk/hardnessofgoldalloysframe.html
http://www.gold.org/jewellery/technology/caratage/index.html
http://www.24carat.co.uk/densityofgoldandothermetalsframe.html
Vince Calder
Joyce,
Since gold is so valuble you certainly would want to stay away from
any chemical tests that may exist. The easiest way is to wear the
piece and see if you get discoloration of your skin or the piece of
jewlery. If you do, then the piece is very low in gold content
(most likely gold plated) and probably high in nickel or
copper. You can also tell a lot just by looking at it. Real gold
should be a nice soft yellow and it should not be very shiny. It
will certainly have a sheen to it, but it should not shine. You
can also stick a pin/needle into the gold. If the pin breaks then
it is not real gold--gold is soft and maleable.
Some might suggest that you take the density of the jewlery, but the
problem is that your jewlery is not pure gold. 14K gold is 14 parts
gold and 10 parts other metals. Since you do not know exactly what
those other metals might be, you cannot tell by taking the
density. For a chemical test, which I do not suggest, you can scrap
a small portion of the jewlery off with a razor blade. You can get
HCl (hydrochloric acid) or H2SO4 (sulfuric acid) at a hardware store
and drop the scrappings into a small amount of the acid--use a piece
of glass to do this on. If the metal dissolves completly, then
there is no gold. Whatever does not dissolve is gold. Just be
careful, acid can seriously burn you, eat through your clothes,
damage most things that it touches and can even eat away your drain
pipes! Remember that some of it should be expected to dissolve,
since 14K gold is only 58% pure.
If you can stop by or call some local jewlery shops, they might be
able to perform a gold test for you by taking an X-ray of the
piece. The charge for this, if any, should be less than $20.
Matt Voss
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Update: February 2012
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