Abstract
IN 1904 Prof. A. Verneuil published an account of his successful experiments on the artificial reproduction of ruby. He pointed out at the time that his method of crystallising was of considerable commercial interest, but at first most attention was paid to producing decorative gems. The watch-making industry was the first to adopt these gems for the bearings in watches. Their uniform colour and moderate price have led to their general adoption in this industry. In a paper on “Synthetic Corundum for Jewel Bearings” by E. G. Landmeier, published in the Journal of the Institution of Electrical Engineers for May, a description is given of the manufacturing processes used in the production of rough synthetic corundum and of jewel bearings for electric meters and other measuring instruments. A description is also given of the methods now used for the synthesis of sapphire. It was stated that it is difficult to obtain natural stones as hard and as uniform as synthetic ones. A few years ago, practical men found it difficult to believe that synthetic stones grown in the chemical laboratory in a few hours could equal natural stones. It has to be remembered that special processes have now made it possible to obtain for the synthesis of corundum raw material of the highest purity, which is only rarely found in Nature. Numerous photographs are shown illustrating the effect of a rotating pivot on the jewel. Communications from several engineers discussing the author's conclusions are published at the end of the paper. Manufacturers of meters apparently are not yet agreed as to the relative lengths of the lives of the synthetic and natural jewel bearings.
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Synthetic Corundum for Jewel Bearings. Nature 132, 344 (1933). https://doi.org/10.1038/132344c0
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DOI: https://doi.org/10.1038/132344c0