Alchemy and Gold Crystals

Name: Max
Status: student
Grade: 9-12
Location: England
Question: I am a student studying alchemy. I would like to confirm
my thoughts on the subject by asking: Is it possible to make pure
gold (crystal structure face centred cubic FCC)? I do not think it
is as I would have thought gold is a pure element and therefore it
cannot be copied by alloying etc.?
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Indeed you can make or grow gold crystals without too much trouble
assuming the proper supplies and training.  The process of making the
crystal will often purify the gold.  You can make a crystal from it by
either melting/annealing or by chemical deposition from solution.  The
first method requires a supply of reasonable quality gold and a torch
(among other things).  melting the end of the wire will cause the gold
to bead up and form a liquid ball.  If the liquid ball is cooled slowly
(and in a uniform direction) then if has a reasonable chance to
crystallize in a single lattice.  Often in practice you will get a twin or
triplet, but there are a few tricks you can use to improve your chances.
 The surface may not show much or any direct faceting (even through a
microscope), but an x-ray diffractometer can quickly verify its
condition.  During the heating and melting process many of the
impurities will be burned off by the torch and many of the others will
be forced to the surface during annealing.  Repeated application of the
heating and cooling can be used to improve the purity.
Heating and holding the entire crystal at just below the bulk melting
point of gold will also improve the quality.

You can also create gold crystals just as you would salt or sugar
crystals, though you use particular acids instead of water.  There are
two ways to do this, either by creating a super-saturated solution
directly by temperature differences or by changing the concentration
(evaporation).  The gold then comes out of solution (slowly) and
crystallizes.  Depending upon the conditions, you can many (thousands or
more) tiny crystals, or just a fewer but larger ones.

In our lab, we are very interested in the properties of gold and gold
crystals (and other metals).  On several occasions we have actually made
our own crystals by the first method.  Typically we can get them up to
around 1cm on side in raw form.

Most gold that you find around you is alloyed to some extent.  Among
other things this is done to harden the gold into a useful state.  It
will also be polycrystalline.  Pure gold crystals are extremely soft and
very easy to destroy.  They really are not much stronger than a warm
stick of butter(maybe that's not exactly true, but they are darn soft).
 A fall of just a few centimeters is all that is needed to turn a gold
single crystal into a mashed up gold poly-crystal.

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Michael S. Pierce
Materials Science Division
Argonne National Laboratory
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