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
23 Jan-15:33:40 Re: mysterious red pyramids in mexican opal (Amir Akhavan)
23 Jan-14:06:49 Re: collection of firmo espinar (Firmo Espinar)
23 Jan-09:34:11 Re: mysterious red pyramids in mexican opal (Michael Shaw)
22 Jan-22:14:41 Re: mysterious red pyramids in mexican opal (Ahallenbeck)
22 Jan-22:12:43 Re: mysterious red pyramids in mexican opal (Ahallenbeck)
22 Jan-10:46:19 Re: collection of michael shaw (Michael Shaw)
22 Jan-01:12:29 The mizunaka collection - quartz (Am Mizunaka)
21 Jan-15:12:48 Re: a mineralogical trip through italy by sante celiberti (Sante Celiberti)
21 Jan-06:36:29 Re: collection of volkmar stingl (Volkmar Stingl)
21 Jan-06:14:53 Re: mysterious red pyramids in mexican opal (Riccardo Modanesi)
21 Jan-00:12:54 Re: mysterious red pyramids in mexican opal (Volkmar Stingl)
20 Jan-20:38:41 Re: mysterious red pyramids in mexican opal (Alfredo)
20 Jan-20:28:43 Re: mysterious red pyramids in mexican opal (Bob Harman)
20 Jan-19:28:19 Mysterious red pyramids in mexican opal (Ahallenbeck)
20 Jan-13:48:45 Re: synthetic rubies and shortwave uv (Riccardo Modanesi)
20 Jan-04:24:07 Re: pectolite? from maoping quarry, wuyishan, china (Volkmar Stingl)
20 Jan-03:43:08 The mizunaka collection - quartz (Am Mizunaka)
20 Jan-03:40:48 Re: the mizunaka collection (Am Mizunaka)
19 Jan-22:35:19 Re: the mizunaka collection (Jim Wilkinson)
19 Jan-22:12:47 Re: schorl (Jim Wilkinson)
19 Jan-21:43:17 Re: synthetic rubies and shortwave uv (Rgangue)
19 Jan-21:08:41 Synthetic rubies and shortwave uv (Tom Mazanec)
19 Jan-17:42:44 Re: pyrite with bubble-like growths (Roger Warin)
19 Jan-17:38:30 Re: schorl (Roger Warin)
19 Jan-11:29:53 Re: collection of firmo espinar (Firmo Espinar)

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
77641


The time now is Jan 23, 2021 17:49

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.
Natural heat treating
  
  Index -> Off-Topic and Introductions
Like
1


View previous topic :: View next topic  
Author Message

Tom Mazanec




Joined: 11 Feb 2016
Posts: 118
Location: Twinsburg, Ohio

View user's profile

Send private message

PostPosted: Dec 26, 2020 18:41    Post subject: Natural heat treating  

Do wildfires ever "heat treat" gems?
Back to top
Reply to topic Reply with quote
Like
   

alfredo
Site Admin



Joined: 30 Jan 2008
Posts: 824


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 26, 2020 19:01    Post subject: Re: Natural heat treating  

Heat treatment requires very slow heating and cooling to avoid cracking crystals by thermal shock. I think wildfires probably come too fast.
Back to top
Reply to topic Reply with quote
Like
   

Riccardo Modanesi




Joined: 07 Nov 2011
Posts: 570
Location: Milano

View user's profile

Send private message

PostPosted: Dec 27, 2020 03:34    Post subject: Re: Natural heat treating  

Hi to everybody!
A Bunsen flame is normally used to treat gemstones by heating. It works with pale brown topazes (turning to pink), amethysts (turned to citrine) and weak grey tanzanites (turning to vivid blue and/or violet). I had an experience in Idar-Oberstein some decades ago.
Greetings from Italy by Riccardo.

_________________
Hi! I'm a collector of minerals since 1973 and a gemmologist. On Summer I always visit mines and quarries all over Europe looking for minerals! Ok, there is time to tell you much much more! Greetings from Italy by Riccardo.
Back to top
Reply to topic Reply with quote
Like
   

mmauthner




Joined: 30 May 2007
Posts: 110
Location: Graz

View user's profile

Send private message

PostPosted: Dec 27, 2020 05:20    Post subject: Re: Natural heat treating  

Well, Alfredo, I am not sure about that. In fact, I am convinced that wildfires can produce heat-treated crystals. That said, I am not convinced the results in the case I have in mind were desirable.

Many moons ago, I was digging for quartz crystals at Crystal Park in Montana, I found an area that had a number of crystals in the soil/decomposed granite, but they were devoid of color---completely colorless. As I dug deeper, the crystals I found had color, which improved with depth. I did not apply strict scientific methods at the time; that is, I did not get out a tape measure and exactly record the depth of each find, but my memory has it that the colorless crystals occurred in the top 40-50 cm and the best color was at about a meter depth (one was only allowed to dig to 4 feet). When I stepped back to look at the "section", I noticed that the "zonation" was also defined by charred and non-charred roots. Remembering what I had been told about baking amethyst in bread to avoid thermal shock in heat treatment, I came on the idea that a wildfire had raged here (also evidenced by older charred stumps, etc) and crystals within the top 40-50 cm got hot enough to lose their amethyst-smoky color.

I also remembered that in the case of smoky quartz and amethyst, heat treatment reverses the effect of natural irradiation that causes this coloration in quartz, GIVEN pre-existing chemical conditions in the quartz. I then took things further, in that I had a contact back at the University that operated a Co-60 autoclave, and had him re-irradiate a couple of the specimens, and LO! the colour came back! The interesting thing is, and this perhaps speaks to the pre-existing conditions I mentioned---the resulting color was somewhat pale, so we tossed the pieces back into the autoclave for improvement (an entire weekend) but got no more color out of it, so I believe that the color we achieved is actually the 'original' color.

By the way, we performed all kinds of cool experiments with the autoclave...for my thesis, I tested the tenebrescence of the spodumene from my thesis area: pink to green, back and forth several times, I think we were also the first to produce the raspberry red apatite from Pakistan (very early 1990's). A friend had left his apatite on window sill and the pink color completely disappeared after a few months, and after talking to him about my experiments with my thesis apatite, he asked if I would bring back the color on his apatite. Well, I confidently told him 'sure,' of course thinking it would also bring it back to 'original' color. Well,...surprise!!

Unfortunately, again, I did not apply rigorous scientific method in that I did not record exact exposure durations, radiation strengths, Brand name of the autoclave, take pictures of the hole in Montana, complete with survey rod, etc, etc. so I never formally wrote up my findings, as was later suggested to me by another scientist who lived in a publish or perish world.

Anyway, a long answer to say that, yes, forest fires can affect the color of minerals.
Best,
Mark
Back to top
Reply to topic Reply with quote
Like
   

Amir Akhavan




Joined: 01 Dec 2009
Posts: 55
Location: Hamburg

View user's profile

Send private message

PostPosted: Dec 27, 2020 18:19    Post subject: Re: Natural heat treating  

Interesting observation, Mark. 300-400°C would be enough and pale the crystals within a few hours, higher temperatures would work much quicker.
_________________
Amir C. Akhavan, Hamburg, Germany
Back to top
Reply to topic Reply with quote
Like
   

alfredo
Site Admin



Joined: 30 Jan 2008
Posts: 824


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 27, 2020 20:55    Post subject: Re: Natural heat treating  

Mark, I think that would be a rare and very localized occurrence in Nature - perhaps in some spot where a large tree fell and burns for a few days, or where campers have built an all-night fire in a fire ring. But in general the heat of a forest fire only penetrates a couple cm into the ground. Google soil temperature profile in wildfires.
Back to top
Reply to topic Reply with quote
Like
1
   

James Catmur
Site Admin



Joined: 14 Sep 2006
Posts: 794
Location: Cambridge


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 28, 2020 09:06    Post subject: Re: Natural heat treating  

I tend to agree with Alfredo. I find it hard to believe a wildfire could affect a mineral's color

alfredo wrote:
Mark, I think that would be a rare and very localized occurrence in Nature - perhaps in some spot where a large tree fell and burns for a few days, or where campers have built an all-night fire in a fire ring. But in general the heat of a forest fire only penetrates a couple cm into the ground. Google soil temperature profile in wildfires.
Back to top
Reply to topic Reply with quote
Like
   

Bob Morgan




Joined: 18 Jan 2018
Posts: 112
Location: Savannah, Georgia


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 28, 2020 09:38    Post subject: Re: Natural heat treating  

As a fire fighter I would not be surprised at the temperatures that might occur. I have no particular knowledge of wildfires, but the temperatures in house fires commonly rise above 2000 F. Too much water applied produces unbelievably high temperature steam that pushes downward and penetrates even fire gear.
There. I've shared my ignorance.
Back to top
Reply to topic Reply with quote
Like
   

Matt_Zukowski
Site Admin



Joined: 10 Apr 2009
Posts: 648
Location: Alaska


Access to the FMF Gallery title=

View user's profile

Send private message

PostPosted: Dec 28, 2020 11:02    Post subject: Re: Natural heat treating  

In soils with peat or other undecomposed organic matter (a large volume percent of dead tree roots perhaps), forest fires move underground, and so would the thermal effects. One sees this in Alaska and Siberia where forest fires move underground for the winter and then reappear above ground when the surface soil dries out.

It seems to me an open question as to how rare it is to find tree roots penetrating a xl-bearing regolith in sufficient quantity and in a way that can burn and cause the phenomena observed by Mark.
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 2006-2021


Powered by FMF