Page:A treatise on diamonds and precious stones including their history Natural and commercial.djvu/179

 APPENDIX.

IMITATIONS OF COLORED STONES.

THE pink variety of the Topaz being considered the most valuable and beautiful, many impositions have been practised in making imitations of it. The most common is to form a doublet of a white topaz, and to introduce a little color between the pieces. When this manufactured gem is finely cut and close set, it bears a strong resemblance to that which it is intended to imitate; nor will the measures generally adopted to detect fraud in other stones avail here, as, being a topaz, it is inferior neither in hardness nor in lustre to the real gem. If the jewel is close set, and the table very low, this imposition can only be discovered by drawing the stone from its setting, when it will appear perfectly limpid, except in the part where the color is introduced: but if the table is high the fraud may be detected by holding the jewel horizontally between the eye and the light, as the part exposed will then appear perfectly diaphanous.