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Offline wus47Topic starter
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« on: April 27, 2013, 09:54:08 am »
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   Some days ago I have found in mountains a fragment similar to bronze. But there were also rusty splinters of a shell. But this splinter had not traces of corrosion and was of red color. I have measured density of this fragment (11.2 g/cm3) and it has appeared too large for bronze (11,2 г/см3). If it was the alloy of copper and lead that the colour of this bronze should be white. Instead of red. At polishing this fragment it shines as gold. At account of density of an alloy of copper and gold at measured density (11.2 g/cm3) of a fragment , percentage of gold should be about 30 percents.
  I understand that the most authentic answer would be the spectral analysis. But it is expensive for me.
  Can somebody answer my question on an alloy of copper and gold?  
  Images this fragment are placed below. This fragment was found near to old fortification (has remained only stone masonry).
Size of fragment 35x19 mm. Thickness from 1.5 mm to 3.5 mm. Weight 11.2 g.
Was found near Rome limes in Ukrainian Carpathian (my hypothesis) and it is (possible) a rest of statuette.

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« Last Edit: April 27, 2013, 10:04:04 am by wus47 »
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« Reply #1 on: April 27, 2013, 10:45:43 am »
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Time for the good ol Gold Test Kit. Shocked

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Offline xavier
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« Reply #2 on: April 27, 2013, 11:29:58 am »
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Hi Wus47

Have you tried to find other pieces? The color would indicate a high percentage of copper but copper would not break like that as it is too soft. Brass and other such hard alloys will break like the piece that you have there. In other words I'm at a loss mostly because of the color of your splinter.

All the best
Xavier       

Posted on: April 27, 2013, 06:26:25 PM
I had another look at you piece and at closer inspection it does have the color of brass in some palaces, it looks like it's just the outside that has this red copper color so I would say that it's a kind of brass.
 

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« Reply #3 on: April 27, 2013, 11:33:22 am »
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It does look like brass but the Patina was a bit light.   Huh??

Just thinking.    A Acid test would sort that out Pronto!

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Offline xavier
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« Reply #4 on: April 27, 2013, 11:51:10 am »
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Yes but what would you test it for in the first place? if it's old enough there could even be silver it there.

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« Reply #5 on: April 27, 2013, 10:36:28 pm »
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If Wus47's calculations are correct and the gold content is around 30%, that would make it 7.2 karat (24 x 30%). My gold test acid can only test to as low as 9 karat (37.5% gold), and I'm not aware of any acid test kits that go lower than that (would love to get one that can go down to 2-3 karat, if available).

Quote:Posted by wus47
I understand that the most authentic answer would be the spectral analysis. But it is expensive for me.

If by "spectral analysis" you mean x-ray fluorescence, I'd not rely on it. Yes it is expensive, but you get fast results only of the surface of the object, not the inside content. If the metal content of the object is not homogenous, you will get an inaccurate answer. The most reliable method is still the fire assay, but unfortunately that will still cost money.

I know how you feel, Wus47, and I had agonized over it a long time because I frequently encounter naturally-occuring auriferous copper-sulphide ores. Very low gold content! And it is not nice to have to keep paying for professional analysis, so here are my suggestions for no cost tests:

1) Take a piece of floor tile and rub the metal on the rough back side of the tile. Observe the color of the streak produced. If you see gold color in it, then it most probably has some gold in it. Leave the tile alone for a few months. Copper will tarnish, silver will oxidize, but gold will always be noble gold and unaffected. The attached photo is the result of my own test. I left it alone for about 4 months.

You can see the copper tarnishing to green, but there are still flecks of gold that are unaffected. I made the mistake of rubbing more than one section of the ore in the same part of the tile. I now know this ore is not homogenous and each part of each piece must be rubbed in separate parts of the tile, because one part may have little or no gold, and other sections have more gold. That is why one overlapping streak turned greener than another rubbing.

It is important to have a control streak. If you wish, take a piece of known copper and rub it on the tile next to where you rubbed your metal. You can then observe how the copper tarnishes in relation to your metal's streak.

2) Take your piece of metal to a goldsmith and tell him it is low-karat gold and you wish to sell it. He will then run his own tests to see if it is worth anything. Go to 2 or 3 goldsmiths and compare their results and offers.

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Offline wus47Topic starter
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« Reply #6 on: April 28, 2013, 01:15:57 am »
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Dear Xavier!
 Thank for the answer. Then I have not found still similar splinters. But there they should be. I shall try the coming days to go away again on that place. May be today I canl place on Youtube  video about fortyfication (that place, where I have found a red splinter). You nothing have told about density (gravity) of this splinter. It is very much high for a brass or bronze. Only presence of gold in an alloy can have this. high density (gravity 11.2 h/cm3).
There i found a rusty splinter of blade or sabre. Other rusty splinter (top part) of saber or blade (which was found there) I lost .
What You think about gravity?
 What means "Gold test kit"?
Have a nice weekend.


Posted on: April 28, 2013, 01:12:14 AM
Thank You very much for your answer (reply). Yes,  this splinter have homogenous structure. It is visible at crack.
What You think about hign gravity 11.2 g/cm3?
 Some militaries tell me that this splinter may be is a fragment of shell (specific copper alloy).

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Offline wus47Topic starter
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« Reply #7 on: April 28, 2013, 04:19:24 am »
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Dear "Hobbyst"!
Thank You very much for your answer and help. As my error previous reply was placed at Xavier message.
Therefore I thank once again.
Red color the mentioned fragment may be related with my put (dipping) into solution  of nitric acid (one minute).
Bellow are attached few images of fragment of blade.

Posted on: April 28, 2013, 03:47:55 AM
Dear "Hobbyist"!
Once again.
If I have understood you correctly, I should leave streak on a porcelain plate (or back side of the tile or porcelain plate). It is very good advice.
To go to the jeweller too quite good advice. But if this fragment has historical (archaeological) value that the price of the jeweller there will be less of price as antiques.
Have a nice weekend



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« Reply #8 on: April 28, 2013, 08:11:23 am »
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Hello Wus47, I am glad I could help!

Quote:Posted by wus47
Red color the mentioned fragment may be related with my put (dipping) into solution  of nitric acid (one minute).


Yes if you were using dilute nitric acid, you would see the red color in the result.
3Cu(s) + 8HNO3(aq) ——> 3Cu(NO3)2(aq) + 2NO(g) + 4H2O(l)

May you find more treasures!



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« Reply #9 on: April 28, 2013, 03:15:56 pm »
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Can you guys get nitric acid in Malaysia ?

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