I have a strange request here. I need to appraise a lump of metal. It was 'obtained' by a friend from a large-scale precious metal refinery in the UK about 20 years ago. Specifically it was found at the bottom of a smelting crucible.

A small sliver was sent off for analysis several years ago (by a jeweller) who said the analysis showed it contained high content of gold, platinum and palladium. He was happy to keep the small sliver as payment.

The total mass of the lump is just over 600g

Can anyone offer some advice about where it could be taken to determine its exact content? Possibly to sell it.

Kind of clutching at straws, but there might be someone on here who can help.

Hi twatmangle (love the name!)

You need a precious metal assayer - type that into google and start ringing around to see what can be done with your mystery metal, for example:

Cornwall Analytical Services

Regards,
crude.

Analysis will only tell you what is in the sample sent and not what the complete lump is made of. No one would know what processes the lump underwent or how it was cooled. To make a true sample it needs to be re-heated, re-mixed and then selective samples analysed. From that a refiner could tell you how much it is worth to them which will not be as close to spot price for the metals as you would most probably like.

Unlike the US, the UK has very few firms that will process small amounts of metals for the general public. I suggest you talk to http://www.hartnellmetals.com/ but it may be too small for them, if it is then you might want to try http://www.cooksongold.com/ or http://www.goldline.co.uk/refiningProductsPage.page

Only go through the pain getting a sample analysed yourself if you do not feel you can trust these firms but remember that the refiner has always been called the last liar. If they say it has been refined and they got this amount of metal out of it and the rest was slag, you will not be able to prove that they were lying regardless of what analysis you had performed.

Fingers crossed it's what you've been told. Those metals are valued in the 10s of thousands a kilo!

Thanks to all of you for the links, I'll pass them on. (It's not actually mine, but a friend's.)

The lump was the the residue of a large crucible and therefore is covered in slag on the outside, but if you slice into it, you get shiny stuff, which hasn't tarnished in 10 years. The problem I have is that it is not consistent so calculating the density won't help.
A quick back of a fag-packet density calculation gives the density of less than 10g/cc but there is a lot of fluffy stuff on the outside padding out the volume, whilst adding nothing to the mass.

Click to view attachmentClick to view attachment

The 'owner' has a furnace so I suggested he melts off fractions. The lead will separate first, then gold then iron etc... this would help purify it a little more, and perhaps he could tap off the slag to cleanit up a little but.

A nice little project this is turning out to be...

Nice lump!

Bit difficult to melt off fractions as the melting points of some of these metals are very close and even with a temperature controlled furnace it will be difficult as the metal has alloyed. You would have to heat to 1,800 c to melt the platinum and then drop to 1,600 c and hold at that temperature to let the platinum solidify, tap off, then drop to and hold at 1,500 c to let the any iron solidify, tap off, and then down the range till you have an ingot of each metal. Lot of work but if you have the furnace and can control the temperature then give it a go!

The only other choices for home brewed refining are acids. Do you self a favour here, don’t do it unless you really want to spend a lot of time on safety. You will need to heat the acids to get the reactions that you need and some of the fumes that can come from it are literally, deadly!

Smashing the crap out of the lump and floating of the slag off should be fun, exercising and reduce your enthusiasm for the project. It will purify it a bit as well