Actually, the various amber colours do occur naturally from yellow
to red to green - even blue! (from the Dominican republic). But
these are rare and as you know a lot of amber is synthetic these
I think I may have written about this, I may not have posted it
Want red amber?
Want blue amber?
See also, other colors.
Want bulk Baltic amber, how much?
Here are two good sources of
On heat treatment: This is from a cutting house
http://www.kekgems.com (good source of cut) explaining amber
treatment, they will tell you what they do, but not the instructions.
"Other resources of Amber not from the Baltic region are either
Regions containing Amber, which is not "old" enough to work
properly with it (polish, heat treatments etc.) or Regions that
contain aged Amber but not in commercial quantities and therefore
also being expensive, resp. not available."
"Therefore Baltic Amber is the only amber, being available and
old enough (45-50 million years), to get a cutting job done,
which clients do require. Most of the natural rough stones are
milky, pale or translucent but very light yellow. To match the
taste and the requirement of the consumers, very special
techniques of heat treatment for these stones has been developed,
whereas each company, working with these fine stones, keeps their
developed technique as a secret know-how."
"Just by heating these stones (at low temperature), the
following general changes will appear: If heat and air (as in a
regular stove is the case) is supplied to the stones, the
material will clear up and darken. If stones are heated under a
vacuum (i.e. by an autoclave), stones will clear but not changing
their color towards a darker shade. By special techniques, heat
may cause Glitter to appear inside of the stone." (This also
occurs naturally, most all has a human hand in it though, and if
done right brings better a price than plain.) "Under such a heat
treatment, the natural properties of amber is not changing, so
that such a heat treatment may never be proofed and the amber is
still considered to be a natural Amber."