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Can you identify this metal? We can't!

 
 
Reply Mon 20 Mar, 2017 02:55 pm
Hello!

My brother was metal detecting in a field in Norfolk, UK, and found a very dense, hard lump of metal which we can't identify.

It has a volume of 10 cubic cm (measured using water displacement method) and a mass of 130g, making its density 13g/ccm. It's very hard (ruling out lead) and irregular in shape but its surface is very smooth.

It's slightly magnetic and bluish grey with darker patches of corrosion (?) that clean off after a bit of rubbing with a metal cleaner.

I have photos but don't think I can post them here.

Anyone got any ideas about what it could be??

We're perplexed because it's way to hard (and dense) to be lead but all the metals close to that density are very rare and wouldn't exist in a lump like this (Here's a link to a metal density chart http://www.goldhog.com/specific_gravity_chart_gold_metals.htm)...

Alex
 
dalehileman
 
  1  
Reply Mon 20 Mar, 2017 03:24 pm
@alexsmalley ,
Quote:
don't think I can post them here

Alex don't be afraid, true the a2k software was badly fu for a couple of days but apparently Jes has got it fixed, with many thanks

Quote:
any ideas
My BH says 'ironite,' and she's much smarter'n me; however, she's just kiddin' this time

Apparently it's an iron ore of some kind. You say its surface is smooth but is it perfectly flat
Can you scratch it easily
Tell us its shape

Man, Eng, Blick, Tim, Kat, help
0 Replies
 
rosborne979
 
  3  
Reply Mon 20 Mar, 2017 04:23 pm
@alexsmalley ,
It's probably not a pure element, it's probably an alloy. Maybe iron bronze or iron lead and something else. It might be a bunch of things all together. Did you find it in a slag dump?
0 Replies
 
farmerman
 
  5  
Reply Tue 21 Mar, 2017 05:53 am
@alexsmalley ,
the density throws me off a bit. Scratch it on the bottom of a bowl(where its not glazed). See if it gives a "streak color" .
The only think I can think of as a mineral with slight magnetic proprties is a solid solution mineral called TANTALITE. It has a density for like 8.5 to over 12 (it is a reql salad spwcially if it contains columbite. SOlid Solutions are a real neat bunch of minerl.


Same thing with alloys, the heaviness is the issue. Are you sure of your measurements?

Id knock off a small chunk and give it to a geology program at a U. to run an EDAX or Xray diffraction (most places will do this for free)

0 Replies
 
alexsmalley
 
  1  
Reply Tue 21 Mar, 2017 06:33 am
Hey Everyone,

Thanks for your comments.

Here are some pictures http://bit.ly/2moyPTL

I'm sure on the mass and volume measurements. Mass comes out at 130g on two different digital scales. The error bars for volume are a little larger and I'm getting somewhere between 9ccm (which would make the density a whopping 14.4g/ccm) and 10ccm on repeated measurements.

It's very hard - I can put the slightest of scratches in it when pressing with a really hard sharp knife, but that feels like I'm just scratching the atoms-thick surface corrosion.

It was found in a field in an area in which we know bronze-age, Roman and medieval populations have all settled. My Brother regularly finds artifacts from these periods (coins, buckles etc) but nothing like this. He would have discarded this as a piece of junk had it not been for its unusual density - which was immediately apparent.

I scratched it on a bowl and it left black streaks which easily rubbed off...

Alex
rosborne979
 
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Reply Tue 21 Mar, 2017 10:37 am
@alexsmalley ,
I don't know. This is going to get out of my league quickly at this point. I still suspect it's some type of alloy or amalgam or something, but I have not way to tell for sure. Farmerman is your best bet on this one.
farmerman
 
  4  
Reply Tue 21 Mar, 2017 10:54 am
@rosborne979,
I think youre right Ros, from the looks of it, it looks like a "pig iron blob"
BUT, that density is a lot
One of my places I did lab analyses of rre erth metals, we had tntalum and iron mixes that looked like that. Were there any weapon plqnts near this site??
farmerman
 
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Reply Tue 21 Mar, 2017 11:04 am
@farmerman,
tantalum metal has a density of about 16.9 (g/c3), so anything that mixes in a solid solution with iron can have a density less than 16.9. So, without anything further knowledge, Ill guess a tantalum mix.
NOW tantalum, especially sintered Ta, had been used in WWII as material in flares that bombers dropped via parachute. Sintered Tantalum , compressed into large pellets and ignited, burns long and extremely bright . A ball, as big as a bowling ball, can be as bright as the sun.
alexsmalley
 
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Reply Tue 21 Mar, 2017 11:30 am
@farmerman,
This is really interesting farmerman!

Just looked up tantalum and the hardness, density and colour of my sample seem to fit, especially if as you suggest it's an alloy of some kind. Its anti-corrosive properties also match - this has been in wet mud for a long time yet came out as shown in the images.

The WWII suggestion also has possible legs - I think Norfolk was used as both an allied air staging post and an axis air target, meaning a military origin is certainly plausible...

Where next? I work at a University so will see if I can get the sample tested and report back.

Thanks for some first class deduction!

Alex

dalehileman
 
  0  
Reply Tue 21 Mar, 2017 11:42 am
@alexsmalley ,
Alex, FMan is really good at this sorta stuff. A rockhound for decades, I wish I had studied it more

At 86 I'm happy to report some of my best specimens will serve to happify the members and customers of my BH's Garden Club. Meanwhile any interested a2k hounds living in the Vicctorville area is welcome to contact me at [email protected]
0 Replies
 
alexsmalley
 
  2  
Reply Tue 21 Mar, 2017 12:08 pm
@farmerman,
Another quick bit of info...

My brother has just confirmed that there was a 29mm Spigot Mortar Emplacement (http://bit.ly/2nGFIQq) on the corner of the field in WWII.

So definitely some military presence with munitions on site...

Alex
rosborne979
 
  2  
Reply Tue 21 Mar, 2017 12:56 pm
@alexsmalley ,
Make sure it's not radioactive before you handle it a lot Wink
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rosborne979
 
  1  
Reply Tue 21 Mar, 2017 01:10 pm
@alexsmalley ,
alexsmalley wrote:
So definitely some military presence with munitions on site...

I had a friend who was a nuclear physicist specializing in armor piercing missiles. He said that during an impact with tank armor the armor and the warhead become liquefied almost instantly and all that matters is the mass/density of the projectile core. So they tended to design a lot of warheads with uranium cores and shells of other high density elements wrapped in various hardness layers. They used fluid dynamic calculations to determine which fluid blobs would be most likely to follow their momentum through the impact node and into the tank.

Not sure that relates to all this, but there's a bit of weapons design theory for you.
farmerman
 
  2  
Reply Tue 21 Mar, 2017 02:12 pm
@alexsmalley ,
it wasnt much of deduction. I first was a rare earth chemist before I worked in mining geology. We used to slightly oxidize "Beta" tantalum qand then compress it into "pills " about as big as a hockey puck. We would then ignite it (that was the hard part), and it would burn like a search lite and leave this gloop that, when it hit the chemical lagoon (HF mostly), it would just go off.
We were just having fun with our skills. Tantalum was used in lots of electronics and battery banks so it can be a fire danger in certain areas so it needs careful handling. Your brother probably found one of the old "Gloops" of melted iron and tantalum.

I used to watch the "detectorists" on BBC , but I quit becaue it got really depressing. These two guys whose only lives were their metal detectors and beer.
0 Replies
 
farmerman
 
  1  
Reply Tue 21 Mar, 2017 04:05 pm
@rosborne979,
sintered depleted U is also "pyrophoric" and getting hit with a metal piercing U shell, is a hell of a way to die.

0 Replies
 
 

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