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Crystallus, Rock-crystal

Crystallus, Rock-crystal Page of 453 Crystallus, Rock-crystal Text size:minus plus Restore normal size   Mail page  Print this page
       
     
 
178
CRYSTALLUS.
 
 

 
 
the same stone is enumerated apparently by him (30) in the list of signet-gems, where, however, it is distinguished from the Crystal, and termed the Hyaloeides. Now, strangely enough, Garcias ab Horto asserts " that no Crystal at all is found in India, but, on the contrary, the Beryl in large fragments, out of which the natives make both glass and vessels of price." The first part of this statement is altogether erroneous, for Crystal is still brought from India, and in masses of enormous size.
Glass had been brought to such perfection when Pliny wrote as to imitate the Crystal with wonderful exactness, yet, strange to say, vases of the latter substance had risen in value, instead of declining through this competition. This colourless, trans­parent glass, approaching as nearly as possible to the true Crystal, was then the most admired. Such probably was the material of the two small vases with handles (pterotas), a dis­covery of Nero's times, that sold for the enormous price of 600 sesterces (60 l.).
The Indians (xxxvii. 20) had discovered the art of forging all the coloured gems, but more especially the Beryl, by staining Crystal. Treatises were extant, says Pliny (75), directing how to stain Crystal so as to pass for the Emerald and other trans­parent precious stones ; but he declines to point them out, on the ground that even luxury ought to be protected against fraud ; adding that no other mode of cheating in the world was so lucra­tive. Dutens, however (Pierres Précieuses, p. 67), is less scru­pulous ; stating that a Crystal made red-hot and plunged re­peatedly into the tincture of cochineal becomes a Ruby ; if into tincture of red santal, it takes a deep red tint ; into tincture of saffron, a yellow like the Topaz ; into that of Turnesol, it assumes the colour of the Sapphire ; into juice of Nerprum, it takes a deep violet like the Amethyst ; and into a mixture of tincture of Turnesol and Saffron, it becomes an imitation of the Emerald. Crystal may also be coloured by the dry method by placing the pieces upon orpiment and arsenic mixed together in a crucible, and so exposing them to heat. The cold method consists in steeping the Crystal in oil of turpentine saturated with ver­digris, or spirits of wine holding dragon's blood or other coloured resins in solution, the depth of tint produced being proportioned
 
 

 
       
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