The Synthetic Production Of Rubies
By W. A. Schildkncht
During the last few years, practically all of the beautiful minerals of
the corundum family have been produced synthetically in the laboratory.
These artificial gems are identical in beauty, hardness, and chemical
composition to those obtained from the mines. The accompanying diagram
shows a furnace commonly used in producing the gems.
The operations are as follows:
A trace of chrome alum is added to a solution of common alum, the chrome
alum being the coloring constituent. Then ammonia is added and a
gelatinous precipitat of the hydrates of alum and chrome is formed.
This precipitat is filtered off, evaporated to dryness and calcined in a
furnace at a temperature of 1000° F. into an ultimate mixture of alumina
and chromic oxid. The proportion in which these two chemicals occur in
the ruby are:
The mixture is then ground into a powder and placed in the hopper "A."
"B" is an electrical tapper which shakes the powder thru the sieve "C"
into the tube "D." Thru this tube the oxygen is also supplied. Hydrogen
is supplied thru the tube "E." The two gases are ignited at "F." "G" is a
platform made of a highly refractory substance against which the flame
strikes and on which the ruby is formed in a pear-shaped mass. The rate
of flow of the powder and the temperature of the oxy-hydrogen flame must
be regulated very carefully.
When a bead of sufficient size has formed the heat is gradually lowered
so that the gem may be free from great stresses. When it has cooled, it
is broken off the base and sent to the cutter who finishes the gem.
It is important that the ingredients used in producing the minerals be of
the purest obtainable.
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