color in blue spinels

[chrono]

Date: 4/4/2010 1:39:07 PM
Author: colormyworld

Date: 4/4/2010 1:36:29 PM
Author: Harriet
Is it known yet whether the Luc Yen material contains cobalt?

From what I have read, they are colored by Ti+ Fe

CMW,
I thought it was coloured by Cr(+x?) and Fe+3?

 

[chrono]

An interesting question that I’m not sure has a definitive answer yet. I know that iron gives the most beautiful colour in many gemstones, yet also causes some browning in others? I own 2 certified cobalt spinels and know that both are coloured by both iron AND cobalt because the memo states it as such. I’ve also read the hauyne like Luc Yen blue spinels are coloured by iron AND chromium. It could also be a different form of iron (as it oxidizes) that causing both the good and the bad (Fe+2 versus Fe+3)?

I prefer to think of a gray mask in any stone as tone without much saturation, although there is always the possibility of a chemical structure that is causing it.

ETA,
I just read all the responses and see that I have parroted Empress perfectly.

 

[LD]

Date: 4/5/2010 9:37:51 AM
Author: Chrono

An interesting question that I’m not sure has a definitive answer yet. I know that iron gives the most beautiful colour in many gemstones, yet also causes some browning in others? I own 2 certified cobalt spinels and know that both are coloured by both iron AND cobalt because the memo states it as such. I’ve also read the hauyne like Luc Yen blue spinels are coloured by iron AND chromium. It could also be a different form of iron (as it oxidizes) that causing both the good and the bad (Fe+2 versus Fe+3)?

I prefer to think of a gray mask in any stone as tone without much saturation, although there is always the possibility of a chemical structure that is causing it.

ETA,
I just read all the responses and see that I have parroted Empress perfectly.

Or the actual amount of iron present.

 

[Barrett]

don''t think it''s anything to do with structure..also known as psuedochromatic coloration..the dispersion ones are only diamond and zircon maybe sphene if i am not mistaken and the scattering ones don''t apply..asterism, adularescence, etc...good point chrono..could be lack of sat. which leaves space for something to fill the void and gray would fit as it''s a blending of the prime colors..gray and nature go hand in hand but the number one cause for any color and stones is transition elements so it only makes sense to take the chemical formula and remove any that you know can''t or won''t cause gray and see what you have left..it''s like..well we know chromium causes red in many stones as well as green as a fact..managanese almost exclusively causes red in stones as a fact..we know for a fact that in aquamarine gray is caused by iron so only makes sense to impart the same thought process on spinel that certain transition elements track records dictates..what an interested thread..good job CMW..this type of thread makes you read up and double check info you normally wouldn''t bother with..great learning and very educational

 

[colormyworld]

Date: 4/5/2010 9:33:27 AM
Author: Chrono

Date: 4/4/2010 1:39:07 PM

Author: colormyworld

Date: 4/4/2010 1:36:29 PM

Author: Harriet

Is it known yet whether the Luc Yen material contains cobalt?

From what I have read, they are colored by Ti+ Fe

CMW,

I thought it was coloured by Cr(+x?) and Fe+3?

Good catch Chrono. You are right. I think I just have a hard time accepting the chromium part because it brings such a beautiful red or green to most other stones. Go figure. It is strange though in other spinels chromium is red. I guess it is a combination of the other elements that cause the blue. What a gorgeous blue it is in those spinels from Vietnam. Like others have noted, very much like hauyne.