Quantcast
  We apologize for any slow response. This will be fixed before October 31st Portal logo
Login/Register
Bactrian Gold Treasure from Afghanistan, coming soon....
/gemstones/streeter-precious-stones/page_256 - 2
 

Sec. III, Ch. 11: Turquoise

Sec. III, Ch. 11: Turquoise Page of 366 Sec. III, Ch. 11: Turquoise Text size:minus plus Restore normal size   Mail page  Print this page
232                               The Turquoise.
Vivianite, with which it is impregnated. It is easily distinguished from the mineral or true Turquoise, by emit­ting an odour when gently heated. It is, also, softer and more opaque than true Turquoise. It differs entirely from the mineral in composition and structure, and it rarely, if ever, loses its colour. The bony structure may be detected under the microscope. Abroad the fossil Turquoise is more esteemed than in England, in conse­quence of its freedom from outward change, but it is not so valuable as the Rock Turquoise.
The other mineral often mistaken for Turquoise is Callainite—a substance which far more closely resembles the true gem than does the Odontolite. It is, however, of a lighter colour, and has not the peculiar optical properties of the Turquoise. The Turquoise has a translucency peculiarly, its own, reflecting light from under its surface ; it also easily receives a brilliant polish. The Callainite, on the contrary, is a duller stone, not so vivid nor so fine in colour.
Beads and other ornamental objects in a greenish mineral much resembling Turquoise have occasionally been unearthed from the ancient sepulchral monuments with which the land of Brittany abounds. About 30 years ago M. Damour, the eminent French chemist, analysed some specimens from near Lockmariaker, in the Mor­bihan, and finding them to be a phosphate of alumina, of green colour, indentified them with Pliny's Callais, and suggested a revival of the old name. Dana afterwards proposed for this substance the modified Plinian name Callainite, but more recent researches have proved its identity with the mineral called by Breithaupt Variscite.
Some interesting discoveries of Variscite, in the form
Sec. III, Ch. 11: Turquoise Page of 366 Sec. III, Ch. 11: Turquoise
Table Of Contents bullet Annotate/ Highlight
Streeter: Precious Stones and Gems
Suggested Illustrations
Other Chapters you may find useful
Other Books on this topic
bullet Tag
This Page