Talk:Sapphire
from the Antique Jewelry University
re: synthesis of flame fusion blue corundum
1800: the basic identity of ruby and sapphire was identified
1817: Guy-Lussac found that heating ammonium alum would obtain pure aluminum oxide. Synthesizing corundum was on its way!
1837: A series of experiments began with Gauding, Fremy and Verneuil. No success as they did not have the technology to maintain consistent temperatures needed: 2050°C
1876: Verneuil became Fremy's lab assistant and some crystals were reliably and repeatedly produced.
It could be argued that since experiments were conducted with several flux agents like potassium hydroxide and barium fluoride,the final product, although described as rhombohedral ruby crystal was actually red, violet, and bluish in color. (*Kurt Nassau, Gems Made by Man, Fremy's Work, p. 39) Ruby synthesis was understood and repeatable. The Al+3 would simply be replaced by trace amounts of Cr+3 and a ruby would result every time. Further experiments produced xls of several tones of "bug juice", which could technically be termed sapphire, even though they were not a fine blue color. The problem: Creation of various colors (aside from red) were not repeatable as the chemistry of the specific chromophore, needed to obtain colors other than red, was not understood at that time.
1909: Paris firm of Abraham A. Heller, supplier and manufacturer of imitation stones (doublets, imitation pearls, and the new synthetic ruby) wanted to add synthetic blue sapphire to their bag of tricks. They hired Verneuil to head their lab, as they were quite confident he would be able to sort out the chemistry.
Verneuil began testing sapphires and found the blue ones consistently contained iron and titanium. He found that the addition of iron and titanium in place of chromium would reliably produce the desired blue result. (in this case, 2 Al+3 atoms would be replaced by one each Ti+4 and Fe+2)
Two US patents were awarded to Verneuil, and his employer, the Heller Company on 3/28/1911 and 9/26/1911, described as "closely resembling natural sapphires as possible" and "having beneath its surface bubble-like spots bounded with rounded walls."
It was not until 1968 that the actual mechanism behind the color of blue sapphire was explained as intervalent charge transfer, but the precise chemistry of BLUE sapphire is still a matter of some debate within the mineralogical community.
re: (Tim) I was thinking that all this in depth info about synthetics would be better placed on its own page. An article like ' sapphire' should be a portal for loads of deeper info reached by various links. No?
Cross referencing and timeline
I think one of the beauties of a wiki is the cross referencing. This synthetic information also clarifies for many the timeline of synthetic sapphires. I have seen many Victorian pieces set with blue glass that were represented as synthetic sapphire out of ignorance of these facts. As we develop a timeline for AJU this will be integrated there as well. good work!
From: Barbra
I added the info on development of synthetic sapphire. Hope that was OK.
I use esoteric stuff like that to help date jewelry. You can feel free to put it in any context you'd like, or eliminate it entirely.
published
from: Tim I've published the timeline in an unedited format. I'll add inclusion pictures and dress it up in a table at a later date. Got to go hunting for inclusion pics first.