We use cookies to show content based on your preferences. If you continue to browse you accept their use and installation. More information. >

FMF - Friends of Minerals Forum, discussion and message board
The place to share your mineralogical experiences


Spanish message board






Newest topics and users posts
18 May-02:15:24 Re: the mim museum in beirut, lebanon (Tobi)
17 May-22:38:32 Re: collection of volkmar stingl (Volkmar Stingl)
17 May-03:14:23 Re: the mim museum in beirut, lebanon (Mim Museum)
16 May-08:20:07 Re: help with mineral identification in thin section from khibiny, kola peninsula (Daniel Garcia)
16 May-05:41:19 Re: help with mineral identification in thin section from khibiny, kola peninsula (Duncan Miller)
16 May-03:20:17 Re: help with mineral identification in thin section from khibiny, kola peninsula (Daniel Garcia)
16 May-01:49:42 Re: help with mineral identification in thin section from khibiny, kola peninsula (Duncan Miller)
15 May-22:21:35 Re: collection of volkmar stingl (Volkmar Stingl)
15 May-17:34:35 Gilbert gauthier - silvia's collection (Silvia)
15 May-09:05:40 Re: the mim museum in beirut, lebanon (Mim Museum)
15 May-06:13:55 Re: monthly mineral chronicles, mineral guides and more... (Crocoite)
15 May-02:23:13 The mizunaka collection - quartz (Am Mizunaka)
14 May-15:59:22 Re: help with mineral identification in thin section from khibiny, kola peninsula (Daniel Garcia)
14 May-12:47:43 Re: help with mineral identification in thin section from khibiny, kola peninsula (Pete Modreski)
14 May-12:03:14 Re: collection of volkmar stingl (Volkmar Stingl)
14 May-10:40:37 Help with mineral identification in thin section from khibiny, kola peninsula (Daniel Garcia)
14 May-10:25:53 Re: what is it? (Janjasina)
13 May-16:53:55 Re: silvia's collection (Silvia)
13 May-13:18:46 Re: elbaite, ending moor's head (Daniel Garcia)
13 May-10:19:46 Re: what is it? (Amir Akhavan)
13 May-10:18:08 Re: what is it? (Alfredo)
13 May-08:22:44 Re: collection of firmo espinar (Firmo Espinar)
13 May-08:22:07 Re: what is it? (Bob Morgan)
13 May-08:16:44 Re: what is it? (Firmo Espinar)
13 May-07:38:51 Re: what is it? (Fiebre Verde)

For lists of newest topics and postings click here


RSS RSS

View unanswered posts

Why and how to register

Index Index
 FAQFAQ RegisterRegister  Log inLog in
 {Forgotten your password?}Forgotten your password?  

Like
93405


The time now is May 18, 2022 09:05

Search for a textSearch for a text   

A general guide for using the Forum with some rules and tips
The information provided within this Forum about localities is only given to allow reference to them. Any visit to any of the localities requires you to obtain full permission and relevant information prior to your visit. FMF is strictly against any illicit activities related to collecting minerals.
Opal- Heat tolerances
  
  Index -> Off-Topic and Introductions
Like
2


View previous topic :: View next topic  
Author Message

Christine Mathis




Joined: 05 Feb 2022
Posts: 3
Location: Florida

View user's profile

Send private message

PostPosted: Feb 05, 2022 14:25    Post subject: Opal- Heat tolerances  

I have a small broken piece of opal in an unknown rock. While I understand it isn’t a valuable piece, it’s sentimental and I think it would make a nice pendant. I am a ceramic artist, but I’ve only worked with sterling silver clay on a few occasions. I’d like to mold the clay around the stone as well as fill in the fractured areas for aesthetics. My question is if this opal (and unknown rock around it) can it withstand the high temperatures required to fire the clay and withstand the stress of the clay's shrinkage (approx. 10-18%). I've included a picture of my stone and the firing schedule with temperatures.


4C3BAD8C-6F27-4BBB-8870-2D4FB517E1CA.jpeg
 Mineral: Opal
 Description:
 Viewed:  1007 Time(s)

4C3BAD8C-6F27-4BBB-8870-2D4FB517E1CA.jpeg



89107AB0-F853-4769-A3E7-9A3886AC4D42.jpeg
 Description:
 Viewed:  1001 Time(s)

89107AB0-F853-4769-A3E7-9A3886AC4D42.jpeg


Back to top
Reply to topic Reply with quote
Like
   

James Catmur
Site Admin



Joined: 14 Sep 2006
Posts: 981
Location: Cambridge


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Feb 05, 2022 14:32    Post subject: Re: Opal- Heat tolerances  

Opal has water within its structure (which is why some people call it an unlucky stone, as it expands in contact with water so can stretch its setting and drop out), so I would expect it to not survive
Back to top
Reply to topic Reply with quote
Like
2
   

Julie Wilson




Joined: 13 Aug 2020
Posts: 5
Location: Dallas, Texas

View user's profile

Send private message

PostPosted: Feb 05, 2022 15:29    Post subject: Re: Opal- Heat tolerances  

I am far from the expert here but, I will add what information and thoughts that I can.
You have a piece of boulder opal. Usually it is backed by ironstone but this looks like a different variation which I can’t remember the makeup of the non-opal parts.
In many ways what it is has little relevance on the risks and concerns with the idea of heating these stones. They are both opal and two different materials bonded to each other.
Opals do have a water content which makes them inherently more temperature sensitive than most stones. That said, even if it was not opal which concerns me significantly, I would have hesitations about the idea of putting anything like this in an oven. You have two different materials attached to each other that you plan on heating. The concern is that the different materials will have different rates of thermal expansion. If they expand different amounts there is a major risk of cracking.
My suggestion is either you learn or have someone else set these pieces more like a typical cabochon. You can either set them with a thin strip of silver between the pieces or, do a repair/re-construction using reliable non-yellowing adhesive. You say that the value is sentimental. This is why, in my opinion, the question becomes about your desires rather than any “best practices” or “best value” concepts that do not stem from avoiding a risk of damage or failure of the stone over time.

On a side note…The comment above about being “unlucky,” is something that, although some have heard and believe, I work hard to dispel. According to the well-respected, opal auctions website:
This rumor started as a literary fiction is the early half of the 1800’s. A book by Sir Walter Scott wrote a book called "Anne of Geierstein,” which single-handedly caused a massive decline in opal sales. This is the first instance of opals being associated with bad luck and is a work of pure fiction. To make things worse, in 1874 Charles Dickens wrote a short story called "The Opal Ring." This second work of fiction including opals as bad luck charms did incredible damage to opal sales. This discrediting of opals is something that is commonly attributed to a DeBeers marketing campaign. After all, DeBeers are responsible for the concept of diamond engagement rings. In fact, among my limited family heirlooms is an opal engagement ring likely pre-dating the books that lead to the rumors. Although DeBeers did not start the rumors about opals being bad luck, but they are credited with fanning the flames and helping ensure the fictional idea became widely accepted.
Best of luck!
Back to top
Reply to topic Reply with quote
Like
   

Christine Mathis




Joined: 05 Feb 2022
Posts: 3
Location: Florida

View user's profile

Send private message

PostPosted: Feb 05, 2022 17:05    Post subject: Re: Opal- Heat tolerances  

Thank you so so much for your thorough response.

I came here because I am clearly out of my area of expertise :) You have a wonderful and knowledgeable community!!!

I wanted to know if it could be done because I’ll have more pride in the outcome if I do it myself. Unfortunately, it looks like silver clay is not the right option and I’ll have to explore an alternative setting method or take it to a professional.

The added background information was an awesome bonus. It was fascinating to learn about the history!

Thanks again :)
Back to top
Reply to topic Reply with quote
Like
   

SteveB




Joined: 12 Oct 2015
Posts: 218
Location: Canberra

View user's profile

Send private message

PostPosted: Feb 05, 2022 19:15    Post subject: Re: Opal- Heat tolerances  

Definitely no heating but look into Kintsugi or maybe find someone who does it. It's the Japanese art of pottery repair using gold mixed with lacquer and is quite spectacular, but as a first time DIY project you’re likely to make things worse trying it yourself. But I think gold with this piece would look awesome. Maybe a local lapidary club can help with the repair, the cracks will be there forever though, and you are likely to make matters worse on your own. Mineral repairs are a trade skill all its own. Just grabbing epoxy from the hardware store is not going to work. Depends how serious you are about the piece and your sentimental attachment to it. But someone who does Kintsugi would make it whole again and beautiful too, not sure about the strength but would look awesome on a shelf for display, wouldn’t trust it for wearing no matter what there are going to be more cracks already in those pieces and changes in temp and humidity are likely going to cause further breakage in those other cracks, unless you reassemble and encase entirely in epoxy. Again, speak to people who do these things, don't look up Wikipedia and think that sounds easy unless you want to ruin things.
Back to top
Reply to topic Reply with quote
Like
   

alfredo
Site Admin



Joined: 30 Jan 2008
Posts: 905


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Feb 06, 2022 00:09    Post subject: Re: Opal- Heat tolerances  

Christine, At the temperatures you indicate, your opal would definitely be destroyed. You'd end up with some white dehydrated silica that would be hardly any more beautiful than a piece of chalk. You'll have to fire your ceramic setting BEFORE you insert the opal.
Back to top
Reply to topic Reply with quote
Like
   

James Catmur
Site Admin



Joined: 14 Sep 2006
Posts: 981
Location: Cambridge


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Feb 06, 2022 07:30    Post subject: Re: Opal- Heat tolerances  

Julie Wilson wrote:
On a side note…The comment above about being “unlucky,” is something that, although some have heard and believe, I work hard to dispel. According to the well-respected, opal auctions website:
This rumor started as a literary fiction is the early half of the 1800’s. A book by Sir Walter Scott wrote a book called "Anne of Geierstein,” which single-handedly caused a massive decline in opal sales. This is the first instance of opals being associated with bad luck and is a work of pure fiction. To make things worse, in 1874 Charles Dickens wrote a short story called "The Opal Ring." This second work of fiction including opals as bad luck charms did incredible damage to opal sales. This discrediting of opals is something that is commonly attributed to a DeBeers marketing campaign. After all, DeBeers are responsible for the concept of diamond engagement rings. In fact, among my limited family heirlooms is an opal engagement ring likely pre-dating the books that lead to the rumors. Although DeBeers did not start the rumors about opals being bad luck, but they are credited with fanning the flames and helping ensure the fictional idea became widely accepted.
Best of luck!


My wife had an opal ring and she used to do the dishes with it on. After two stones had dropped out she stopped - maybe for the wrong reason. Our jeweller explained why he thought the stones dropped out (water absorption). Maybe they were just badly set and it was nothing to do with the nH2O causing them to expand the settings
Back to top
Reply to topic Reply with quote
Like
   
Display posts from previous:   
   Index -> Off-Topic and Introductions   All times are GMT - 5 Hours
Page 1 of 1
    

 
Jump to:  
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 vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum


All pictures, text, design © Forum FMF 2006-2022


Powered by FMF