Dive into anything

I'll be doing a good bit of metal detecting this year and I always find a ton of scrap metal, especially stuff like old nails. I'd really like to learn how to melt these down into ingots for later use.

I find copper, brass, lead, aluminum and other random bits of metal all the time while detecting so I'd like to be able to smelt those too. Like last time I went out I found 2 old brass padlocks.

So I'm looking for a crucible that can handle iron but I have no idea what material I'll need, a quick googling suggests silicone carbide but I want to verify it.

What about size? Any issues with going a bigger then needed for later use or is it better to go with small and just get larger ones later?

I also found two chunks of 'mystery metal' at the site where an old farm house burned down back around 1980ish. Pictures here. I can take some more if it'll help.

It's very hard, coated in a white corrosion/oxide that pretty tough to get off. There's some specks of green discoloration up under the white stuff.

I thought it was aluminum at first but after dropping it in a pot of molten aluminum for around an hour it never got soft or melted so it has a melting temp significantly over 1220f.

It's parametallic. A magnet will stick to it but it won't attract anything itself. I used an angle grinder with a metal cutting disc and it ate up my disc faster then it cut into it. I can cut through 1/2" iron chain with that disc no problem.

I've been using a a heavy iron file (after those pics) to remove some of the white stuff but the it's wearing my file out pretty quick. Way too hard to be lead or silver. Melting temp too high to be zinc or magnesium.

Which leaves (as far as I know..) Something like stainless steel, nickel or titanium. Nickel seems unlikely as it would be magnetic, right?

I'm thinking bout taking this over to the local uni to ID. My curiosity is off the charts right now. Odds are theres more of this stuff in that spot too, I just did a cursory search and turned up all kinds of melted blobs of stuff but most of it I could ID easily.