Mindat.org Conference 2014 Madagascar 28 May 2014 - 13 June 2014
Welcome to the GemologyOnline.com Forum
A non-profit Forum for the exchange of gemological ideas
It is currently Sat Apr 19, 2014 9:13 am

All times are UTC - 4 hours




Post new topic Reply to topic  [ 27 posts ]  Go to page 1, 2  Next
Author Message
 Post subject: High and Low Zircon
PostPosted: Sun Mar 11, 2012 11:25 pm 
Offline
Valued Contributor

Joined: Thu Sep 24, 2009 3:44 pm
Posts: 120
Location: Portland, Oregon
Hello everyone,

I have been a member for quite some time, but am just now to the point of being able to understand some of what I have been reading and researching.
I am learning gemology through this board and several books.

I am a lapidary and faceter, which has led to my interest in gemology.

I have googled and done a board search here to see if I could get a grasp on the differences between High and Low Zircon.
Also what are the types (low or high) that are generally used in jewelry.

Sorry if this is a dumb question.

Thanks Harold


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Mon Mar 12, 2012 12:40 am 
Offline
Gemology Online Veteran
User avatar

Joined: Fri Oct 30, 2009 9:19 pm
Posts: 593
Location: Las Vegas, NV
This might be of some help to you, particularly the fourth paragraph.

http://www.bwsmigel.info/GEOL.115.ESSAY ... ircon.html

_________________
-Ryan Quantz, A.J.P. (GIA)
-Lapidary and Jewelry Artist
http://www.etsy.com/shop/RyanQuantzStudios


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Mon Mar 12, 2012 5:23 am 
Offline
Moderator
User avatar

Joined: Thu Dec 13, 2007 3:42 pm
Posts: 4011
Location: the Netherlands
Let's take a look at that paragraph:

Quote:
Some zircon crystals contain naturally radioactive thorium and uranium. Over time, this radioactivity breaks down the crystal structure so that such stones (always green) tend to an amorphous, glass-like state, with a lower refractive index and luster than the crystalline type. These unenhanced gems are referred to as "metamict" and are sought after collector's items.


Always green? Is that true? In my experience you can turn it around: all green zircs are metamict* (fancy lingo for 'low' which means the crystal structure is degenerated by the presence of radioactive elements. High zircons have their crystal structure intact because they are younger or contain little or no uranium) but I'd be very cautious to state that all metamict zircons are green. In my experience they are often brown or brownish orange.

The paragraph further states that over time, the crystal structure 'tends to an amorphous (glass-like) state with a lower RI' (I dunno about the luster, luster is such a subjective criteria, dependent on polish, cleanness etc that I would rather see that bit gone too). What happens is that the neatly arranged atoms (Zr and O) 'break out of their densely packed positions' (the crystal structure) due to the radiation emitted by uranium (and, apparently, thorium) impurities, thus affecting the optical density of the material. It's getting less dense and therefor 'bends' (refracts) light to a lesser degree (lowers the RI). High zircons further have a high birefringence, what do you think happens with that in low zircons?

Something else happens when atoms 'break out of their densely packed positions'... Something which we can measure and commonly use in gemology. Can you figure out what that would be, Harold? The answer lies in the question, take a good look at the words that are used.

* apparently this is incorrect as well: although many greens are indeed metamict, high greens exist. Now that earthling mentions it: I should have known that, he showed me green zircs with wicked spectra, indicating a high state.

_________________
Antique Jewelry University - Your online source of information on antique and vintage jewelry.


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Mon Mar 12, 2012 6:16 am 
Offline
Valued Contributor

Joined: Tue Oct 17, 2006 11:33 am
Posts: 358
Location: New Zealand
Quote:
Some zircon crystals contain naturally radioactive thorium and uranium. Over time, this radioactivity breaks down the crystal structure so that such stones (always green) tend to an amorphous, glass-like state, with a lower refractive index and luster than the crystalline type. These unenhanced gems are referred to as "metamict" and are sought after collector's items.

as Tim mentioned this is not a correct fact. Green low and high Zircon have been documented. Also as mentioned there are low type Zircons with olive-brown-yellow color.
Further there is also the intermediate type that is often overseen.
Intermediate Zircon displays a lower degree of metamictization and is not entirely amorphous but is mostly not recognized and classified as low Zircon

_________________
Gemstein.com


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Mon Mar 12, 2012 6:43 am 
Offline
Valued Contributor
User avatar

Joined: Wed Dec 30, 2009 11:44 am
Posts: 442
Location: PAKISTAN-Peshawar
Dear HHelton, please click the below link and you will understand better the High and low zircon
http://attawaygems.com/NMFG/Lets_talk_g ... zircon.htm


with best regards

HUK

_________________
Gemology for everyone.
Hamid Usman Khattak (HUK)


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Mon Mar 12, 2012 6:52 am 
Offline
Moderator
User avatar

Joined: Thu Dec 13, 2007 3:42 pm
Posts: 4011
Location: the Netherlands
Ollie, have you heard of high greens?

there you go... so my: 'all greens are metamict' can be disregarded...

_________________
Antique Jewelry University - Your online source of information on antique and vintage jewelry.


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Mon Mar 12, 2012 7:16 am 
Offline
Valued Contributor

Joined: Tue Oct 17, 2006 11:33 am
Posts: 358
Location: New Zealand
Hi Tim

Yes there is a documented piece of Alan Hodgkinson that I saw in person.

_________________
Gemstein.com


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Mon Mar 12, 2012 11:26 am 
Offline
Valued Contributor

Joined: Thu Sep 24, 2009 3:44 pm
Posts: 120
Location: Portland, Oregon
Quote:
Something else happens when atoms 'break out of their densely packed positions'... Something which we can measure and commonly use in gemology. Can you figure out what that would be, Harold? The answer lies in the question, take a good look at the words that are used.


There are a couple things that I would think would happen that could be noticed.
First, they might have a lower SG as they are no longer Densely packed.
Second, I would think that the deterioration (as they "break" out of their densely packed positions) would be noticible as scaring or inclusions.

My mind pictures a gem deteriorating and as the atoms break their tight bond I would think the gem would actually expand, therefor becoming less dense.

Are low zircons, which seem to me to be less desirable passed off in the gem world as high Zircon.

I will check out the links offered and thanks for the help.

Harold


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Mon Mar 12, 2012 11:53 am 
Offline
Moderator
User avatar

Joined: Thu Dec 13, 2007 3:42 pm
Posts: 4011
Location: the Netherlands
Quote:
First, they might have a lower SG as they are no longer Densely packed.
My mind pictures a gem deteriorating and as the atoms break their tight bond I would think the gem would actually expand, therefor becoming less dense.


Exactly! :smt023

Quote:
Second, I would think that the deterioration (as they "break" out of their densely packed positions) would be noticible as scaring or inclusions.


Although they can be 'milky' usually transparency doesn't change. Amorphous substances can be perfectly transparent, think glass...

Quote:
Are low zircons, which seem to me to be less desirable passed off in the gem world as high Zircon.


Nope, nobody in the trade mentions high or low. Actually, nobody in the trade mentions zircons much, I truly wonder where they all end up...

_________________
Antique Jewelry University - Your online source of information on antique and vintage jewelry.


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Mon Mar 12, 2012 3:19 pm 
Offline
Site Admin

Joined: Thu Jan 05, 2006 4:27 pm
Posts: 1690
This is the bit that blows me away...as the SG lowers the physical size of the zircon changes...these babes are growing all the time.


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Mon Mar 12, 2012 6:47 pm 
Offline
Platinum Member

Joined: Tue Nov 29, 2005 2:02 pm
Posts: 2647
From an investment standpoint, I would be VERY cautious from the growth potential. :)

Sorry Frank. :P


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Mon Mar 12, 2012 10:10 pm 
Offline
Gold Member
User avatar

Joined: Mon Apr 16, 2007 12:05 am
Posts: 1249
Frank wrote:
This is the bit that blows me away...as the SG lowers the physical size of the zircon changes...these babes are growing all the time.


I like how this process can help to identify zircon inclusions in other gemstones... seen as stress halos arising from the expanding inclusion. I recall Conny had a nice picture of this.


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Mon Mar 12, 2012 11:23 pm 
Offline
Valued Contributor

Joined: Thu Sep 24, 2009 3:44 pm
Posts: 120
Location: Portland, Oregon
Well I have actually learned and retained a good bit of new Info.
Thanks everyone.
I really like that Tim asked a question that made me have to think about the process that creates the Low Zircon, and I would love to see the photo of a Zircon inclusion (wasn't even aware they existed).

Also learned why the few Zircons I have cut looked fuzzy and generaly yucky when I thought they should be gorgeous. Will make sure to cut the next one perpendicular to the C axis.hope I said that right [-o<

More questions to come.

Thanks Harold


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Tue Mar 13, 2012 12:49 pm 
Offline
Gold Member
User avatar

Joined: Mon Apr 16, 2007 12:05 am
Posts: 1249
Zircon inclusion in sapphires posted by Tim (scroll down the page) and posted by Conny (again, scroll down the page).


Share on FacebookShare on Twitter
Top
 Profile  
 
 Post subject: Re: High and Low Zircon
PostPosted: Tue Mar 13, 2012 1:39 pm 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 14026
Location: San Francisco
For those who can't bother to click through:
Tim's image of a zircon crystal with stress fractures in a sapphire:
Image
and Conny's with what appear to be stress fractures eminating from the inclusions:
Image


Share on FacebookShare on Twitter
Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 27 posts ]  Go to page 1, 2  Next

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 1 guest


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