Question about Montana Sapphires...

[CaraMish]

I have a lovely very clear and bright Montana sapphire cut by Daniel Stair, Jr. Gorgeous stone, and very interesting too: It has a tiny area of yellow in the centre of the stone. So, technically, it''s a bi-colour. I know this light yellow area is common in Montana sapphire, but I''d like to know how it happens-how the crystal develops this way...

Is it perhaps due to iron content???

Thanks in advance for any help...

 

[kcoursolle]

I''m afriad I don''t know much about what causes the inclusions, but I would love to see a pic of your sapphire and it would probably help the experts to see a picture. I bought a stone once from Dan and it was stunning. He is great to work with.

 

[CaraMish]

Date: 8/27/2006 1:20:14 AM
Author: kcoursolle
I''m afriad I don''t know much about what causes the inclusions, but I would love to see a pic of your sapphire and it would probably help the experts to see a picture. I bought a stone once from Dan and it was stunning. He is great to work with.

I''ll try to take a pic tonight, but it''s not an inclusion; it''s an area of yellow coloured sapphire in the centre area of the stone. I''m guessing faceters try to place the light area as close to centre as possible for symmetry and colour.

I''m not sure my camera will pick it up-it''s not very noticeable-very interesting characteristic though...

 

[Richard Sherwood]

Hi Cara. Corundum is an allochromatic mineral which derives its color from modifying elements picked up within the host structure while crystallizing. An allochromatic mineral will appear clear or white without these color modifying elements.

Corundum is the allochromatic mineral aluminum oxide (AL2O3). If it has enough iron as a modifying element it will appear yellow. If it has enough titanium as a modifying element it will appear blue. Mixtures of the two will produce colors from yellow to green to blue.

The red color of ruby is derived from chromium as the modifying element.

When you have a crystal with growth sections of different colors, it means that different modifying elements were available to the host crystal as it crystallized. Your stone might have started out with (only) iron available to it, creating the yellow section of the crystal, and then had enough titanium become available to create the blue section of the crystal.

 

[oliver]

hy
imine for sapphires in australia and we have the same phenomena and we call it a pharaos eye!
enjoyur stone

 

[widget]

"Pharaos Eye".... interesting!

I''d love to see a picture of one of these!

widget

 

[oliver]

it happens as the cristal crows and first down the a axis yellow developes ant then later due to change in the trace elements a secondary color,hope that helps.
will post a picture soon

 

[oliver]

sorry wanted to wright c axis

 

[CaraMish]

Date: 8/27/2006 11:34:55 PM
Author: Richard Sherwood
Hi Cara. Corundum is an allochromatic mineral which derives its color from modifying elements picked up within the host structure while crystallizing. An allochromatic mineral will appear clear or white without these color modifying elements.

Corundum is the allochromatic mineral aluminum oxide (AL2O3). If it has enough iron as a modifying element it will appear yellow. If it has enough titanium as a modifying element it will appear blue. Mixtures of the two will produce colors from yellow to green to blue.

The red color of ruby is derived from chromium as the modifying element.

When you have a crystal with growth sections of different colors, it means that different modifying elements were available to the host crystal as it crystallized. Your stone might have started out with (only) iron available to it, creating the yellow section of the crystal, and then had enough titanium become available to create the blue section of the crystal.

Thank you very much, Mr. Sherwood! Very interesting!!!!

 

[CaraMish]

Date: 8/28/2006 4:04:19 AM
Author: oliver
hy
imine for sapphires in australia and we have the same phenomena and we call it a pharaos eye!
enjoyur stone

Yes, I would love to see a pharaoh''s eye!