Within striking distance of home, and a convenient part of my daily exercise, I found this nodule in the stream at Worth Furnace. Noting how heavy it seemed, I took it home to clean it up. I found it was attracted to a magnet, and also that it both attracted and repelled a compass needle. Unfortunately, I checked this after I had stuck the magnet near it so do not know of the polarity of the item was induced by me, or whether it was there beforehand. I carefully cut the end off (hit with a hammer and chisel), and inside you can see it is heterogenous mix of oxides, slag (the shiny bits), and cavities. I suspect it contains little metallic iron, if any at all, and the magnetisim is down to magnetite, an oxidation product. It has that characteristic sulphurous smell you get when cleaning up really rusty cast iron. My guess, based on my limited research, is that this is part of a "bear" - the cruddy lump you get at the bottom of a furnace afer the last firing, or a failed firing. Any further knowledge would be most welcome. The furnace seems to have been fairly short-lived, in the second half of the 16th century, and provided ordnance (balls) rather than cannon.

Photograph:

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Hi this in my opinion looks like a typical siderite iron ore!
It would have changed over the years to give magnetite and goethite!

OK, but there are bits of glassy slag in it?

As if you state there are bits of glassy slag in it then then the other obvious identity is that,it is a partially reduced iron, ore!

I plan to go and record the section through the bay soon, as the stream has made a pretty good job of exposing a clean face. I'll look for another bit of this - there is a huge amount of slag so this bit rather stood out from the rest.

I returned a few days ago and recovered another lump from the stream.
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This one has not been near a permanent magnet, but does affect a compass and has magnetic polarity. The left end in this image is where I exposed the inside, and at this end there is metallic iron, which oxidised within a few hours to the state in this photo. Knocking a few more bits off has not revealed any more of the same. This is the end that affects the compass the most.

The sectioned bay is not as clean as I remembered so a detailed section is not practical without disturbing it which I won't be doing. The whole area could be worth recording as there are distinct ground features. Even though the London Brighton Railway may have disturbed one end of the bay, and possibly other parts of the site, I think there is a lot of archaeology here that has been left largely undisturbed since the furnace last worked - ca 1600?

There are also a few curious "holes" not too far away that show up in lidar scans which may be sources of iron ore. That's me sorted for a couple more excursions!

Oh i do love a bit of slag. I have a piece in my kitchen that I picked up from beside a stream, where a rabbit had been digging.

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I've got a couple of interesting lumps that I found some time ago, though I'm struggling to remember where - possibly Rotherham area, but I pick up so much stuff I just have piles lying around now. I guess it's only half-useful without a location. One is definitely roughly-cast iron, with some small bits of slag or other impurities still embedded. It attracts a small magnet equally well all over the lump, which is very random.

The other is more interesting and is square-ish lump of what looks and feels like solid iron - it's very heavy for its size, fine-grained and orange-brown. This one has what appears to be an encrustation (it may go deeper) of pyrite - or at least a gold-coloured and very reflective mineral, in patches all over. If that's the case, could it still be a result of smelting, or would any pyrite be long gone? If it's not smelted (it doesn't look smelted) and is 'natural', I'm not sure what it is. This lump only attracts the magnet (a strong neodymium one) in one area, and then only weakly, compared to the other.

I only have a medium-range macro lens, so I'm not sure how close I could get to these lumps to be useful - they'e about 40mm across.

I found a larger (80-90mm) long lump of slag recently in the 'Bolehills' area of Cobnar Woods at Meadowhead, but whether it's literally from there is another question. It certainly looks like the lump pictured earlier. That one would be easier to photograph too, if anyone's interested?

It's easy to make mistakes too - a few years ago I found what I was convinced was a 'meteorite' on Bradwell Moor near Hazard Mine - it was black and burnt-looking and was partially embedded in the ground, appearing to have hit with some speed. It was strangely sharp and spiky-looking though, and didn't have the bubbled look of high-speed re-entry. I took it home and spent a good half-hour washing it until it became silvery, but stained a kitchen towel blue every time I dried it. It was a sharp 'fragment' somewhat akin to a curved piece of flint in shape.

Anyway, a guy I know took it to a mate in a steelworks with a XRF gun and he came back with ferro-molybdenum, and wondered where the hell we got it. When we told him the location he was baffled - until we realised that the glassy lumps of slag we'd also found were probably from land 'restoration' after the opencasts had been filled in, and no doubt some of the materials were of interesting vintage. I though ferro-molybdenum was quite expensive though, so an odd place to find it dumped.

I'd be interested in seeing a photo Phil, the placename suggests pre-17th century lead smelting but the description sounds more like an iron smelting slag. Could well have been both going on in the area at various times, there's loads of slag from bloomery smelting in Wharncliffe Woods if you look at what's eroding out of the footpaths and I'm sure there are many other areas around Sheffield where you can find the evidence of bloomeries if you look.

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Here's some photos - first of the slag - no.1 is on the day I found it, and the others taken today. It's very light, weighing only 69g, and feels like holding pumice:

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Next is both the 'iron' lumps together in my hand for scale - the right one is the 'smelted' piece and is very magnetic all-over, weighing 149g. The left one is the 'pure iron' and is weakly magnetic in one area only, and very heavy, weighing 198g:

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Some close-ups of the 'smelted' piece - sorry for the blurriness - best I could do:

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And a few of the other lump, with the pyrite patches visible. I'm wondering if it's actually a solid lump of pyrite with an oxide crust hiding most of it. Would it be that heavy if so?

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hi this piece looks not too dissimilar to the other one. is it possible for you to carry out a specific gravity test on the two, separate samples?

The slag lump looks like a mixture of slag and part-smelted ore, hard to say without actually seeing it though. I'll have to come round to yours with a hand lens once those of us who aren't Dominic Cummings are able to visit other people's houses...

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I have nothing more sophisticated at home than a small graduated flask, but both 'iron' lumps displaced exactly 25 ml of water, as close as I could get. I re-weighed them on some better scales and got 147.8g for the 'smelted' lump and 192.9g for the 'natural'. So for density that works out at 5.912 and 7.716. That's pretty much spot-on for pure iron, and I guess the smelted lump will have enough impurities to bring that one down. But if it is pure iron (as in, manufactured), why has it got pyrite crystals on it?

I wish I could remember where I found these, but I don't think they were together. I suspect the smelted lump is a piece I picked up near Hoober Stand on the Wentworth (Fitzwilliam) estate near Rotherham.

I find this very interesting; nearby in the bed of a stream is a large piece of what I think is iron slag, (by its rusty colour) there is no proven history of metalworking apart from a street name - Steel Road - and an obscure historical document stating that peat/turf was used to smelt iron (the road nearby is Turves Green ) I should stroll up to the lump of slag and test it with a magnet

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