TY - JOUR
AU - Tully, B J
AB - !CHE PROPERTIES OF PRECIOI'S S'1'OSES. BY Mn. B. J. TULLY. .ABSTRACT.) Delivered on Becember 1Gth, 1909. MR. B. J. TULLY had ken announced to lec- ture on the optical properties of precious stones, but he apologised at the outset by saying that he had ken under some misapprehension in the matter of the subject, and although the optical side would be dealt with, he would deal more generally with the properties of precious stones. A11 precious stones, he said, to the exclusion of pearls, were of mineral origin. They were selected for their beauty and rarity, and the quality of possessing suffircient durability to render them suitable for purposes of personal adornment. They were sub-divided as precious and semi-precious, although there was no defi- nite line of demarcation. The lwauty uf a gem was not manifest until the cutting nnd polishing had been carried out. Then its individual colour and lustre kame apparent, and it was upon the degrees of colour and lustre that the value depended. Beauty niiglit depend upon both colour quality, as in the c8se of the rich ruby, or on total absence of colour as in the pure white diamond. The pro- perty of hardness 
TI - The properties of precious stones
JF - Transactions of the Optical Society
DO - 10.1088/1475-4878/11/1/303
DA - 1909-01-01
UR - https://www.deepdyve.com/lp/iop-publishing/the-properties-of-precious-stones-d5kM1AijE7
SP - 26
VL - 11
IS - 1
DP - DeepDyve
ER -