32 
J. H. BOAS : 
In the author’s opinion a reconstructed or synthetic 
ruby is a ruby. This term means simply a collection of 
chemical and physical properties all of which are possessed 
Jby the laboratory gems. The question was discussed as 
to whether a court of law would hold it a fraud if such stones 
were sold as rubies without any qualifications. 
Incidentally it was mentioned that there was great 
difficulty in obtaining good specimens of rubies. Most 
stones sold in Perth as rubies are really spinels. 
In the case of emeralds, there is no difficulty in detecting 
the artificial stones. These are sold as reconstructed 
emeralds, but all those examined were made by fusing the 
proper constituents with oxide of chromium. All attempts 
at making synthetic gems which contain silica have till 
the present failed. The results are not crystalline and are 
easily distinguished on examination with the dichroscope. 
The physical properties of the so-called reconstructed 
emeralds were also examined, and show clear differences 
from those of the natural stones, as is seen from the follow ing 
figures : — 
Refractive Index Specific Gravity 
Natural Emerald 1.57-1.58 2.69 
Reconstructed Emerald 1. 53-1. 54 2.96 
Finally, the question of the color of the gems was 
briefly touched on. Heaton suggested in his paper that 
the colour of the ruby may be due to chromium aluminate 
in solution, or to metallic, chromium in colloidal suspension. 
The latter idea is most improbable, because the chromium 
is added as oxide and the action carried out in a strongly 
oxidising atmosphere. 
Chromium oxide is also the colouring agent in the 
emerald, and the author’s idea was that in this case the 
chromium functions as a base, in the presence of the acidic 
silica forming chromium silicate. The colour is then due 
to the presence of chromion. In the ruby the chromium 
acts as an acid to the basic alumina and forms aluminium 
chromate, the colour being due to chromanion. 
Experiments to test this idea had been carried out, 
and were still in progress, but no crucial test had yet been 
found. 
