ARTIFICIAL RE-CONSTRUCTED AND SYNTHETIC GEMS. 31 
The following problem was considered. Reconstructed 
and synthetic gems have apparently the same properties 
as those of the natural gems. They are as oeautiful and 
as durable. Is it possible by careful examination of their 
physical properties to distinguish between these laboratory 
products and the natural stones ? 
The author’s examination had been delayed for some 
months until the arrival of a Herbert Smith refractometer, 
and in the meantime this work had been done by Noel 
Heaton and his results described before the Royal Society 
of Arts. 
A great number of stones had been examined, and 
careful examination showed that in the case of rubies the 
reconstructed and synthetic stones had exactly the same 
physical properties as those of the natural gems. Chemical 
analysis also fails to show any difference. The following 
figures illustrate this : — 
Specific Gravity. 
Real Rubies 3.9-4. 1 
Reconstructed Rubies . . 4.00-4.05 
extreme readings from 
16 measurements. 
Synthetic Rubies 4-4-1 
4 measurements 
Refractive Index. 
1.765 . . . 
I.760-I.770 
extremes from 
16 measurements 
I.760-I.763 
7 measurements 
The colour of laboratory stones is very even and 
generally somewhat paler than that of natural stones 1 
but these latter vary considerably in these respects, and this 
alone is not a sure method of detection. Noel Heaton has 
suggested in his paper as the only possible method of dis- 
tinction the examination of the enclosures, especially gas 
bubbles, under the microscope. The stones are placed in 
cells fitted with a highly refracting liquid in order to do 
away with the difficulty due to reflection from the cut 
facets. [The author used a suitable mixture of methylene 
iodide and benzine in his examination.] 
In natural stones the gaseous inclusions follow the 
lines of growth of the crystals and are more or less irregular 
in shape, whereas in laboratory stones they are spherical. 
As a result of the examination of a great number of 
stones, the author is led to the conclusion that though the 
method is undoubtedly useful as a rule, yet cases occur in 
Which it is valueless. Specimens were exhibited of synthetic 
stones apparently free from gaseous inclusions, and one 
undoubted Siam ruby was shown in which the inclusions 
were perfectly spherical. This being so, it is doubtful 
whether the method is of real value in absolutely deter- 
mining the origin of a stone. 
