COLOURS AND NAMES OF GEMS 19 



8. Experiments with Precious Stones 



A man of science cannot say a word about experi- 

 ments with precious stones nowadays, but he is liable to 

 be misunderstood and represented as having discovered 

 how to make valuable gems out of dirt, or of enormous 

 size, and in vast quantity. Last year the production 

 of a few small crystals by the electrical decomposi- 

 tion of bisulphide of carbon was announced as some- 

 thing to affect the stock market instead of as a matter 

 of interest to a few learned chemists. The crystals were 

 supposed erroneously as it turned out to be diamond. 

 We were also gravely told that a competent French 

 chemist had discovered, and that the distinguished 

 geologist, Professor Lapparent, had communicated the 

 fact to the Academy of Sciences, that the radiation of 

 radium acting on " corindon," or, as we should prefer to 

 write it in England, " corundum " a base, dull, colour- 

 less crystal converts that dull substance into sapphires, 

 rubies, emeralds, and topazes and that the dealers 

 attest the value of the precious stones so produced. 

 This is really great nonsense, and arises from a little 

 confusion in the use of the names of precious stones, 

 and ignorance of what the substances indicated by those 

 names are defects which we cannot attribute to the 

 French chemist, but must suppose to have " crept in " 

 to the reports which crossed the Channel. Corundum 

 is a colourless crystal, opaque or translucent. In 

 chemical composition it is the oxide of aluminium 

 standing in the same relation to that light, white metal 

 as rust or hematite ore does to the metal iron. It 

 would not be at all astounding if by simple treatment 

 we could convert corundum into sapphire or into ruby, 

 since sapphire and ruby have precisely the same chemi- 

 cal constitution as corundum are, in fact, only coloured 

 varieties of corundum. Sapphire is blue, transparent 



