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 Thu Mar 28, 2024 9:29 pm

All times are UTC - 4 hours




Post new topic Reply to topic  [ 62 posts ]  Go to page Previous  1, 2, 3, 4, 5  Next
Author Message
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Wed Oct 27, 2010 8:50 am 
Offline
Established Member
User avatar

Joined: Fri Oct 08, 2010 7:17 am
Posts: 46
Oh, alright O:) I don't know much about enamel, but yeah, I think it is more resin-like on the brooch.

ROM, the orange colour in the agate looks like it has "leaked" into the stone over the ages :) The mother rock must have been iron rich.


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Thu Oct 28, 2010 11:57 am 
Offline
Gold Member
User avatar

Joined: Fri Oct 12, 2007 10:22 pm
Posts: 1117
Location: Virginia
Lyric -

I'm confused by your comment. Do you mean "base metal" rather than "white metal?"

You can do vitreous enamel with silver and white gold (not to mention copper).

_________________
Soil is not dirt.
http://hmmdesign.net


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Thu Oct 28, 2010 1:50 pm 
Offline
Established Member
User avatar

Joined: Fri Oct 08, 2010 7:17 am
Posts: 46
I looked it up :P http://en.wikipedia.org/wiki/White_metal

This 'white metal' alloy my brooch is made of, will melt at around a max of 300dg Celsius/575dg Fahrenheit. So enameling with real glass would be impossible :wink:


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Fri Oct 29, 2010 1:04 am 
Offline
Gemology Online Veteran

Joined: Thu Jul 30, 2009 9:00 am
Posts: 545
Location: new york
Empress,

As Ratna mentioned that his brooch was made of white metal,
I commented that the enamel could not be real vitreous enamel but cold enamel (Epoxy type).

The reason is that white metal (a term use to describe pewter, tin, lead and other low temp melting white metal alloys in costume jewelry) melts at about 575 dg Fahrenheit.
Vitreous enamel melts between 1,380 and 1,560 dg Fahrenheit, so by the time the enamel would start melting, the white metal would probably be vaporized.

You can indeed enamel platinum, silver, copper, green gold, yellow gold, even have some success with pink gold.

There might be some white gold alloys that could be enameled but to my knowlege white gold reacts with the enamel pigment resulting in a very unattractive product.

If one is using sterling silver of gold alloys, it is recommended to deplete the metal before enameling. Of course no need to do so with fine silver or 24K gold.

I hope that it cleared the confusion.


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Fri Oct 29, 2010 1:29 am 
Offline
Gold Member
User avatar

Joined: Fri Oct 12, 2007 10:22 pm
Posts: 1117
Location: Virginia
Thanks - just starting here in all these areas - so sometimes I need explanations.!

_________________
Soil is not dirt.
http://hmmdesign.net


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Fri Oct 29, 2010 6:30 am 
Offline
Established Member
User avatar

Joined: Fri Oct 08, 2010 7:17 am
Posts: 46
lyric wrote:
As Ratna mentioned that his (= HER) brooch was made of white metal

Just had to do that :mrgreen: But you couldn't know O:)

Thanks for the clear explanation :wink:


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Sun Oct 31, 2010 8:03 pm 
Offline
Gemology Online Veteran

Joined: Thu Jul 30, 2009 9:00 am
Posts: 545
Location: new york
Sorry Ratna,

Sorry Ratna. I appologyze for my mistake.
I stand corrected.


Empress,

Real jewelry and costume jewelry are two different worlds that sometimes intersect. It can get very confusihg, even more so if you are new to one or both of them.


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Mon Nov 01, 2010 5:38 am 
Offline
Established Member
User avatar

Joined: Fri Oct 08, 2010 7:17 am
Posts: 46
No problem Lyric :wink:
I'm at fault, as I forget to mention I'm a girl, in my introduction topic :oops:


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Mon Nov 01, 2010 10:19 am 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
Quote:
The reason is that white metal (a term use to describe pewter, tin, lead and other low temp melting white metal alloys in costume jewelry)


Not necessarily...I think one must first define whether they are describing fine or costume jewelry.
I refer to platinum, palladium or white gold as white metal, as opposed to yellow metal...gold.


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Mon Nov 01, 2010 11:17 pm 
Offline
Gemology Online Veteran

Joined: Thu Jul 30, 2009 9:00 am
Posts: 545
Location: new york
Barbra,

You are right, white metal is also a term used in real jewelry to refer to platinum, palladium, silver, white gold, etc...

This was in the context of costume jewelry though and unless one is familiar with it, one would usually think of the precious white metals.
This is why Empress was confused and I was explaining to her what the white metal used in costume jewelry was. I should have said : "white metal is a term ALSO used to refer to pewter, tin, lead and other low melting temperature white metals" .


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Tue Jul 02, 2013 10:35 pm 
Offline
New to the Forum or The Quiet Type

Joined: Tue Jul 02, 2013 9:17 pm
Posts: 2
Location: Los Angeles
Hi There,
Here is a Carnelian Chalcedony or Dyed Chalcedony with the bright orange color and faint color banding that can be seen from the pavilion in darkfield.
I tried to post other pictures of the stone yet the system would not let me. To me this stone has color that is unnatural for Carnelian; it looks more like Fire Opal with no play of color. This stone has an SG of 2.56, RI of 1.53, and is AGG = Chalcedony. Is it possible to determine if this stone is dyed with the spectrometer?
Thanks for looking!

Attachment:
File comment: Banding in Carnelian
carnelian01.JPG
carnelian01.JPG [ 31.3 KiB | Viewed 2368 times ]


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Wed May 27, 2015 6:02 pm 
Offline
Established Member

Joined: Sun Dec 18, 2011 9:16 am
Posts: 19
I know this is a rather old post but I thought I would chime in given the fact that this topic comes up early in the google search when searching for information about natural carnelian. Natural carnelian is very rare to come by. The best place to find it is in Middle Eastern countries like Yemen and Iran that value natural carnelian quite highly. In the Middle East like anywhere else a lot of the carnelian stones are treated (dyed) and most agate enthusiasts detect it by shining a light underneath the stone and looking for parallel lines. There is no special name for carnelian in the Middle East and it is known as "agate". That being said there is also a lot of natural carnelian that is highly sought after especially in the dark red liver color. This comes from Yemen and is quite expensive in comparison to other agate stones. Generally for a large cabochon (8 carats) in that color you are talking about 100 - 200 dollars. I wear a natural carnelian stone from the Middle East daily and I will post some pictures of it. The key is to look for natural inclusions and a cloudy like distribution in the stone when there is light shining through the stone. Natural carnelian will generally never be completely red as is seen in commercial agate that was dyed with a nitrate. Generally you will find shades ranging from orange-red, to red, to honey, to brown, to a liver color depending on the lighting. Remember a lot of those ancient red stones you find in museums were dyed red through a heating process while placing the stone in camel feces (credit goes to the Iranian scholar Al-Biruni for documenting this one thousand years ago).

Anyways I have attached some pictures of my natural carnelian stone that was not treated.

Image
Image
Image


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Wed May 27, 2015 7:05 pm 
Offline
Moderator
User avatar

Joined: Mon Apr 02, 2012 9:31 pm
Posts: 4015
Location: North Carolina
jtres wrote:
Natural carnelian is very rare to come by.

Natural carnelian is really not that rare. I have found it myself on a few occasions in the field. Dyed or heated stones do appear to be common in the trade, but that must be more a matter of getting a large and consistent supply than the material actually being all that rare. Similar to the ubiquity of dyed black "onyx" while actual black chalcedony isn't really that rare either.

jtres wrote:
and most agate enthusiasts detect it by shining a light underneath the stone and looking for parallel lines.

I don't quite see how that would help? Different bands usually have different susceptibility to dyes so you'd be likely to see banding on natural and dyed stones alike.

I really like your stone, though! You have excellent taste.

_________________
Rough and cut classic and exotic synthetic gems:https://store.turtleshoard.com


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Wed May 27, 2015 9:47 pm 
Offline
Established Member

Joined: Sun Dec 18, 2011 9:16 am
Posts: 19
Scarodactyl wrote:
jtres wrote:
Natural carnelian is very rare to come by.

Natural carnelian is really not that rare. I have found it myself on a few occasions in the field. Dyed or heated stones do appear to be common in the trade, but that must be more a matter of getting a large and consistent supply than the material actually being all that rare. Similar to the ubiquity of dyed black "onyx" while actual black chalcedony isn't really that rare either.

jtres wrote:
and most agate enthusiasts detect it by shining a light underneath the stone and looking for parallel lines.

I don't quite see how that would help? Different bands usually have different susceptibility to dyes so you'd be likely to see banding on natural and dyed stones alike.

I really like your stone, though! You have excellent taste.



Thank you very much. First off, I would like to clarify a few things that I didn't explain in detail enough. When I stated carnelian was rare, I meant to say it was rare in the market not in the reserves in the world. It's very common to see stones labelled carnelian, being used in lower quality jewelry. It is typically dyed agate in a red orangish color. In respect to looking for parallel lines, I am not trying to state that there is no banding in natural carnelian, but rather in most dyed agate there is obvious parallel striping without any color change and it is a good indicator that the stone is dyed. In natural carnelian the banding or inclusions would at the very least slightly show some variant in color or in strength of the color. In dyed agate you can see the parallel lines but the dyed color is consistent despite the striping. I have included a picture for detail.

Image


Top
 Profile  
Reply with quote  
 Post subject: Re: CARNELIAN frustrations...
PostPosted: Thu May 28, 2015 12:10 am 
Offline
Site Admin
User avatar

Joined: Sun Oct 16, 2005 12:22 pm
Posts: 21602
Location: San Francisco
I have been taught that most carnelian one finds in the marketplace today is heated as well, albeit without the dung.

Almost 100% (perhaps 100% would be more accurate) of the black "onyx" (aka chalcedony) found in the marketplace, throughout history, has been dyed....sugar, honey etc., for centuries and centuries and centuries. Pliny the Elder was the first to talk about treatments, Al-Biruni was the first to document recipes for treatment. He did not develop them himself, he was informed by Iranian Gem Dealers in the ancient world. Dr. John Emmett has experimented with all the Al-Biruni recipes. They all work, producing the desired results.


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 62 posts ]  Go to page Previous  1, 2, 3, 4, 5  Next

All times are UTC - 4 hours


Who is online

Users browsing this forum: No registered users and 5 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