Dominican Republic Jewelery
By Aamir Mannan.
TURQUOISE (Copper) Figure 8.8 (6C)
thor during the war years, has proved to be a most useful diagnostic in a gem material which is notoriously difficult to test. The absorption spectrum of turquoise,discovered by the au
There are bands of almost equal appearance and strength (as shown by a photograph) at 4320 and 4200 A, of which only the 4320 can normally be seen. Only through thin edges is turquoise translucent enough to allow enough light through to render this violet band visible, but fortunately it shows very well by reflected light. There is a vague band in the blue at 4600 A, which helps to provide a distinctive pattern for the mineral. No bands similar to these have been seen in
any minerals or counterfeits which resemble turquoise in appearance. Turquoise which has been impregnated with plastics material has a more intense colour than normal (though no colouring-matterhas been added). In such stones the absorption band at 4320 A is seen much more strongly than usual. Visual acuity is low in the violet region, and many gemmologists have difficulty in seeing this useful turquoise spectrum. The use of blue
light, concentrated through a flask of copper sulphate solution, is of particular value in this case..........
By Aamir Mannan.
TURQUOISE (Copper) Figure 8.8 (6C)
thor during the war years, has proved to be a most useful diagnostic in a gem material which is notoriously difficult to test. The absorption spectrum of turquoise,discovered by the au
There are bands of almost equal appearance and strength (as shown by a photograph) at 4320 and 4200 A, of which only the 4320 can normally be seen. Only through thin edges is turquoise translucent enough to allow enough light through to render this violet band visible, but fortunately it shows very well by reflected light. There is a vague band in the blue at 4600 A, which helps to provide a distinctive pattern for the mineral. No bands similar to these have been seen in
any minerals or counterfeits which resemble turquoise in appearance. Turquoise which has been impregnated with plastics material has a more intense colour than normal (though no colouring-matterhas been added). In such stones the absorption band at 4320 A is seen much more strongly than usual. Visual acuity is low in the violet region, and many gemmologists have difficulty in seeing this useful turquoise spectrum. The use of blue
light, concentrated through a flask of copper sulphate solution, is of particular value in this case..........
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