Quantcast
  Due to a new server, slow response may occur for which we apologize Portal logo
Login/Register
Bactrian Gold Treasure from Afghanistan, coming soon....
/gemstones/king-natural-history/page_276 - 2
 

Onyx, Nicolo

Onyx, Nicolo Page of 453 Onyx, Nicolo Text size:minus plus Restore normal size   Mail page  Print this page
ONYX.
267
by immersion in hot water. This fact is strikingly exemplified in a tricoloured Agate belonging to myself, of which the two darker bands are completely calcined and chalk-like, yet these, after a short soaking, again become two shades of brown, and as translucent as ever. Winckelmann has noticed the same trans­formation in a stone (P. G. de Stosch. No. 1123) engraved with an Apollo, which from white and opaque becomes brown and transparent after having been worn a few hours upon the finger, in consequence of the penetration of the perspiration of the skin into its porous substance. Not being aware of the cause, he sup­posed the gem to be a Hydrophane or Oculus Mundi, a kind of Opal which goes through a similar change if saturated with water. Similarly another gem of mine, a fine Sard, engraved with a head of Sapor II., filled with white spots owing to a partial calcination, recovers its pristine pure crimson after a few days' wear on the finger.
Ben Mansur describes the Onyx (Dschesi) as divided into two species :—The Bakrawi of three layers : the first, opaque red ; the next white ; the third, transparent like crystal : and the Habeschi, also of three layers—two dark, and a white one between them (the actual ονύχων of the Greeks). " Some are striped, others are not ; in others the stripes are so interrupted that they form curious figures." Interesting also is his notice of the localities yielding it :—" Although the Onyx is found in many places, yet those most valued are dug up on the confines of India and of China." From which it appears that, like the early Greeks, he makes no distinction between the Onyx and the Sardonyx.
In the same measure as the Alexandrian glass-workers counter­feited with astonishing success the natural clouds and polished sin-face of the Murrhina, so did they reproduce with equal skill, in their cheaper material, the precious Onyx vases and the cameo designs embellishing their surface. This was effected by fusing an opaque white coating over the coloured body of the vase ; and by cutting this away where required, the design stood out in relief, usually upon a dark-blue ground. The process, as the marks of the graver show, was precisely that employed in cutting cameo in hard stones. Fragments of large vessels thus adorned are frequently met with amongst ancient ruins. Of the perfect the
Onyx, Nicolo Page of 453 Onyx, Nicolo
Suggested Illustrations
Other Chapters you may find useful
Other Books on this topic
bullet Tag
This Page