# Is It Fire Clay?



## Jason1 (Apr 21, 2012)

I discovered what I think is fire clay in my backyard (upstate SC). Seems to harden overnight but initially feels like play-doh to the touch, maybe a little grainier. Anybody have a comment or some insight? Made a nice small crucible from it but have yet to fire it.


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## NobleMetalWorks (Apr 21, 2012)

You may be able to use that with refractory cement, I don't know for sure though. There are some youtube video's on how to make your own crucibles, some better than others, but you will quickly get the right idea. There are so many different types of crucibles for different purposes that you want to make sure you are making the right one for the right job.

On a side note, has anyone ever come across platinum chemistry crucibles before? I just encountered a set today. :mrgreen:


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## butcher (Apr 22, 2012)

Many soils will form clay and can be fired into pottery, they may work also for refractory if mixed in certain proportions, but refractory is usually chosen for its thermal insulating or conducting value, and many times is a mixture of ingredients to give desired property.

The clay you have there seem to me to be high iron content, and I suspect a sulfide, try incinerating some see if you smell sulfur dioxide gases.

I would not try to melt any of your values in it.


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## dtectr (Apr 23, 2012)

For a different, but possibly more profitable, perspective - some VERY collectable jugs were made of that clay 150 or so years ago, I believe. If this is :
1. A sizable deposit and pretty uncontaminated (not sure if that's a real word? )
2. There are old, dilapidated structures about 
3. These were pottery works in the area at one time 
Then there may be collectable artifacts associated with there deposits. Metal detector and old maps - I'm just sayin'
Treasure appears in LOTS of forms


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## Jason1 (Apr 24, 2012)

dtectr said:


> For a different, but possibly more profitable, perspective - some VERY collectable jugs were made of that clay 150 or so years ago, I believe. If this is :
> 1. A sizable deposit and pretty uncontaminated (not sure if that's a real word? )
> 2. There are old, dilapidated structures about
> 3. These were pottery works in the area at one time
> ...



Thanks. There is at least one old foundry nearby at the Cowpens (a revolutionary war site). In the small hole I dug, I've already found some interesting bricks manufactured by Southern Clay Manufacturing Co. Robbins Tn. which went out of business in 1908 (I think).


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## dtectr (Apr 24, 2012)

Dude! 
I almost never use that word (dude) but it does the job at expressing my excitement- that sounds super promising. 
I've always said that there all kinds of treasure - but a lot of folks get tunnel vision and miss values laying right go front of them. 
An example is the early miners in the comstock - they were constantly having to shovel this blue crud out that kept clogging their sluices they were using to recover placer gold - the "crud" turned out to be silver, the quantities of which far exceeded the placer gold in that region. 
Plus you observe, not just see, you're not afraid to work both in the field and in the library. All part of a formula for success as a treasure hunter. 
Please keep us posted on your progress. 
Dtectr


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## Jason1 (Apr 24, 2012)

I haven't been able to incinerate any yet but that's not a bad idea. I did find some kind of instruction on determining the sand/clay content in what I found. ie. Put the materials in a jar/bottle with water, shake, and allow to settle. The bottom layer is supposed to be sand or other sediment while the top layer is clay. I'm sure its not the most scientific test but it was interesting.


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## DONNZ (Apr 26, 2012)

"I'm sure its not the most scientific test but it was interesting."

It is. 

That's the best and only way to test soil content for clay.

If you use it try to remove all the organic matter, it should float. 

More on the subject:

http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=40&t=13173

Soon I'll have a way to fire my crucibles. I have the need to know.


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## publius (Apr 26, 2012)

Jason1 said:


> I haven't been able to incinerate any yet but that's not a bad idea. I did find some kind of instruction on determining the sand/clay content in what I found. ie. Put the materials in a jar/bottle with water, shake, and allow to settle. The bottom layer is supposed to be sand or other sediment while the top layer is clay. I'm sure its not the most scientific test but it was interesting.


For engineering purposes silt falls between 200 and 600 mesh. Below 600 mesh (600 openings per inch) the fine material is designated as clay. Chemically, Clay is Mg or Ca in mineralogy. Dr. Poe can give a better explanation of the composition.

Your test is a valid test and one that is used with a hydrometer to determine the gradation of fine soils. It is also the way clay has been separated from sand and other debris for centuries.

A test to determine if your clay is suitable for making crucibles would be to form a tall cone or pyramid in a ratio of 4:1 or 5:1 base:height After they have dried, fire it in a kiln that exceeds your melting/pouring temperature by about 25% If the cones sag before reaching the melting point then they are not refractory enough. If they sag only slightly between 110-125% of your pouring temp then the clay may be good to make melting dishes from.

Remember that melting silver in coarse clay crucibles is not advised as the clay will act like a sponge and soak up the molten silver. Experience is a bad teacher as she administers the test before teaching the lesson... :roll:


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## Jason1 (Apr 27, 2012)

publius said:


> Jason1 said:
> 
> 
> > I haven't been able to incinerate any yet but that's not a bad idea. I did find some kind of instruction on determining the sand/clay content in what I found. ie. Put the materials in a jar/bottle with water, shake, and allow to settle. The bottom layer is supposed to be sand or other sediment while the top layer is clay. I'm sure its not the most scientific test but it was interesting.
> ...



Thanks. That is exactly the kind of information I was looking for.


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## DONNZ (Apr 27, 2012)

*CLAY....Can You DIg It? part 1*

http://www.youtube.com/watch?v=mv-6zvI3r4c&feature=related

Part one: Boring, lasted one minute and went to Part two: Slow but some good info.


*CLAY... Can You Dig It part 2.*

http://www.youtube.com/watch?v=v0nK1VZHwGo&feature=fvwrel


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## Jason1 (May 1, 2012)

DONNZ said:


> *CLAY....Can You DIg It? part 1*
> 
> http://www.youtube.com/watch?v=mv-6zvI3r4c&feature=related
> 
> ...


Thanks Donnz, this will come in handy too.

Update. I fired one of those vessels and this is a picture of the bottom


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## Jason1 (May 26, 2012)

Does this look promising?


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## Irons2 (May 26, 2012)

I make my own crucibles.
What I see is the Clay has a lot of minerals that are acting as a flux, which is what caused the drip on the bottom.
Iron is also a very powerful flux at high temperature.
Fire Clay is cheap. If you can find a supplier nearby, a 50 lb bag will cost less than $20 and do a much better job. The biggest cost will be shipping.
On a recent order, the shipping was about the same as the cost of the materials. I recommend Cedar Heights Goldart for general use. It's primarily Aluminum Silicate and is quite clean as well as being inexpensive. For a Grog, I suggest Molochite or Mullite, 
The best clay is Kaolin based with very low iron content. If you you use a formula for a cone 10+ Porcelain, it will do well for melting Gold and Silver. Tile #6 Clay with Molochite for Grog fires white and will take over 3000 deg. F.
One thing I can say about making your own crucibles, is to expect spending a lot of time working out the details. It takes time to learn a new skill, even with the best materials.
As a Nag once said: " Anybody can buy Paint."


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## Anonymous (May 26, 2012)

We have a Rinker Materials near us.There I was able to buy 50lbs of Fire-Clay for $9,and 80lbs of portland cement(I don't remember the price),and a massive bag or perlite for just a few bucks.The perlite is used if you want to make a furnace.


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## DONNZ (May 26, 2012)

May not work as crucibles, but keepers as art. Love the colors, texture and the drips.


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## Jason1 (May 28, 2012)

Irons2 said:


> I make my own crucibles.
> ... I recommend Cedar Heights Goldart for general use...One thing I can say about making your own crucibles, is to expect spending a lot of time working out the details. It takes time to learn a new skill, even with the best materials....



Thanks for the comments everybody. When I discovered I had clay in my 1/2 acre backyard I wanted to see what could be done with it (out of curiosity). I think all of you are right though and it would be better to order material from a professional dealer.

Hope everybody has a great Memorial Day. God Bless America


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