January 24 Through February 4—TUCSON, ARIZONA: Annual show
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Tue Mar 19, 2024 12:29 am

All times are UTC - 4 hours




Post new topic Reply to topic  [ 32 posts ]  Go to page 1, 2, 3  Next
Author Message
 Post subject: The blues
PostPosted: Wed Nov 16, 2005 2:06 pm 
Offline
Platinum Member

Joined: Sun Oct 16, 2005 12:42 pm
Posts: 2591
Shall we start with blue transparent stones and how to quickly indentify them?

Name some stones here and we'll discuss diagnostics.

Let me start with Topaz, Tourmaline, Diamond, Apatite, Benitoite, Sapphire, Zircon.
Add your own ones to this list and we'll start discussing the features for fast identification.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Wed Nov 16, 2005 2:10 pm 
Love it! Can we do a thread for each color?


Top
  
Reply with quote  
 Post subject:
PostPosted: Wed Nov 16, 2005 2:36 pm 
Offline
Platinum Member

Joined: Sun Oct 16, 2005 12:42 pm
Posts: 2591
That's the idea yes.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Thu Nov 17, 2005 1:49 am 
Offline
Moderator

Joined: Sun Oct 16, 2005 12:42 pm
Posts: 2846
Location: Ho Chi Minh City, Vietnam
Can we include the purplish/blue stones like tanzanite and iolite?


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Thu Nov 17, 2005 1:16 pm 
Offline
Platinum Member

Joined: Sun Oct 16, 2005 12:42 pm
Posts: 2591
I'm a guy, so purple is blue to me.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Thu Nov 17, 2005 1:40 pm 
Offline
Moderator

Joined: Sun Oct 16, 2005 12:42 pm
Posts: 2846
Location: Ho Chi Minh City, Vietnam
Spinel and cobalt spinel, afghanite, azurite, aquamarine (some of these might be just a bit too rare to bother with right now).


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Thu Nov 17, 2005 3:07 pm 
Offline
Gemology Online Übergod
User avatar

Joined: Mon Oct 17, 2005 2:39 pm
Posts: 3528
Location: San Francisco Bay Area, CA
What about blue beryl?

http://cgi.ebay.com/2-17-CT-SHINING-UNHEATED-BLUE-BERYL-OVAL-CUT-NR_W0QQitemZ5054704660QQcategoryZ110789QQtcZphotoQQcmdZViewItem

It's quite a bit more "blue" than aquamarine, at least to these eyes...


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Sun Nov 27, 2005 2:56 pm 
Offline
Gemology Online Übergod
User avatar

Joined: Mon Oct 17, 2005 2:39 pm
Posts: 3528
Location: San Francisco Bay Area, CA
Ok, no one's answered... but I've done a bit more poking around and it seems that beryl with the above color is being billed as irradiated. Anyone familiar with this process?


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon Nov 28, 2005 2:50 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 3:36 pm
Posts: 192
Location: San Francisco
There are 2 varieties of blue beryl, aquamarine and Maxixe-type.

In 1917 a variety of deep blue beryl was found in the Maxixe Mine located in the Piaui area south of Arassuahy in Minas Gerais. It was noted that after exposure to sunlight or strong artificial light that this blue beryl would fade lowly but irretrievably. The optical character of this Maxixe-type blue beryl is significantly different from aquamarine. If anyone is interested in the specifics of these differences, let me know.

In 1973 quite a few of these dark blue beryls were showing up on the market again. They had the same anomalies and similarities in optic characteristics to the Maxixe beryl. Kurt Nassau and his colleagues studied these stones and found that their color was due to irradiation and annealing, BUT they faded just like the original Maxixe beryls.



I have recently seen some darker blue beryl available, that is considerably darker in tone than one would expect with aquamarine, but I believe it to be aquamarine as opposed to Maxixe-type beryl. We have a couple pieces in the shop where I work that are similar in color to the stone that Gem-n00b posted. The locality of the material that we have in the shop is reported to be Brazil, and the vendor claims the stones to be untreated. There was a recent find of dark blue aquamarine in Canada:

http://www.gia.edu/gemsandgemology/1857 ... detail.cfm


Ux4 is also in possession of some dark blue stable aquamarine. Perhaps he can share a little more information on it, as to locality and treatment if known.

_________________
"Do well and you will have no need for ancestors" Voltaire


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon Nov 28, 2005 3:02 pm 
Offline
Platinum Member

Joined: Sun Oct 16, 2005 12:42 pm
Posts: 2591
Quote:
If anyone is interested in the specifics of these differences, let me know.

Uh, ofcourse we're not silly :)


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon Nov 28, 2005 3:17 pm 
Offline
Moderator

Joined: Sun Oct 16, 2005 12:42 pm
Posts: 2846
Location: Ho Chi Minh City, Vietnam
Quote:
Uh, ofcourse we're not silly


We're not?


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon Nov 28, 2005 3:21 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 3:36 pm
Posts: 192
Location: San Francisco
:oops: Sometimes I'm silly! :oops:
Dichroism:
Aquamarine: deeper color belongs to the extraordinary ray
Maxixe: deeper color is found belonging to the ordinary ray, while the extraordinary ray is almost colorless

Spectrum:
Maxixe: Strong absorption in the red end of the spectrum (695, 655nm, with weaker bands showing at 628, 615, 581, & 550nm.) (somewhat like zircon!)

Habit and chemistry:
The original maxixe stones exhibited little crystal form, and had high contents of caesium & boron.

Specific gravity:
Maxixe: 2.80
Aquamarine:2.65-2.76

Refractive Index:
Maxixe: 1.5844-1.5920
Aquamarine: 1.564-1.587 (extraordinary ray)
1.579-1.593 (ordinary ray)

_________________
"Do well and you will have no need for ancestors" Voltaire


Last edited by anatase on Mon Nov 28, 2005 4:37 pm, edited 1 time in total.

Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon Nov 28, 2005 4:20 pm 
Offline
Gemology Online Übergod
User avatar

Joined: Mon Oct 17, 2005 2:39 pm
Posts: 3528
Location: San Francisco Bay Area, CA
What kind of fading is noted with these Maxixe-types? Are we talking fading to the color of an aquamarine? Fading to goshenite? Fading to a still-deep-blue-but-not-quite-as-deep-blue-as-before?


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon Nov 28, 2005 4:31 pm 
Offline
Moderator

Joined: Sun Oct 16, 2005 12:42 pm
Posts: 2846
Location: Ho Chi Minh City, Vietnam
Go all the way down to the bottom pictures on this page and you will see a before and after picture of Maxixe type beryl.

Gorgeous photos on the whole page of various aquamarines.


Top
 Profile  
Reply with quote  
 Post subject:
PostPosted: Mon Nov 28, 2005 5:04 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 3:36 pm
Posts: 192
Location: San Francisco
The picture that is used in the above article was taken from the Winter 1998 Issue of G&G, which features a 1 page story on Maxixe beryl that was submitted to their lab for testing.
If anyone is interested in seeing the G&G article, send me a PM.

_________________
"Do well and you will have no need for ancestors" Voltaire


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 32 posts ]  Go to page 1, 2, 3  Next

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group
Gemology Style ported to phpBB3 by Christian Bullock