Undersea metallic nodules-- how strong are they? like solid metal or more like stone? what are they like?

Question

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I'm writing fiction about people who have access to undersea metallic nodules, though I've never seen them in real life.

My characters do NOT have modern metallurgical equipment, or materials processing methods!

Are they close enough to solid metal that you could, for example, attach a handle to one and use it as a sledge hammer? grind or saw an edge on one, use it as an axe?

How heat resistant would they be? Would they bind well to cement or concrete? Could my characters use them as bricks to build a fireplace? Or would they give off nasty odors and fumes? Do they contain sulfides or oxides?

If you tried heating one in a blacksmith's forge, could you work the nickel/iron/cobalt? Would you have to beat them to drive out the copper content & leave behind the other metals?

Obviously, people who cut & paste an irrelevant answer or try to direct me to some wiki article will NOT get Best Answer!

Thanks for your patience in reading all the details

When I refer to beating on the nodule, above, I am thinking in terms similar to hand forging wrought iron. The lump of ore (usually limonite, or bog iron) is heated with charcoal and a bellows in a forge. When it is glowing hot, the smith must take it with tongs, lay it on the anvil, and hammer it. Sparks, which are mostly composed of silica, come flying out; hence we get the phrase 'make the sparks fly" about some intensive process that puts us under pressure. The resulting iron is malleable and suitable for making crude tools.

I do not expect that charcoal and a bellows would make a hot enough temperature to smelt metals like nickel, cobalt, manganese, etc. So I wonder whether the copper content of these nodules might melt first and be driven off as sparks by beating, as with silica in iron, as described above.

While the first answer is not bad, any subsequent answers are greatly appreciated, or if the first answerer cares to add some details. Thanks again!

Answer 1

Polymetallic nodules are iron-manganese (mainly manganese) nodules, grown out of a nucleus by chemical precipitates. It takes millions of years for one to form. They look like a dark irregular shaped object, often having a botryoidal surface. They are usually small in size, reaching upto the size of a potato. If you have ever visited a metal beneficiation plant anywhere and seen a slag fragment, these nodules look more or less like it.
No, you cannot use them as sledge hammer heads - they are not as large or as heavy and definitely not as strong. It may be possible to use them as a small axe, the way you describe, but it will not last for long.
Being metals, they are good conductors of heat and hence cannot be used as refractory material. But they bind very well with cement or concrete, and can be used as bricks provided you make provisions for their irregular shapes. I donot remember them to contain sulphides, I guess it is not likely.
Extraction of metal from them involves normal processes of metallurgy. I don't know what you meant by "beat them to drive out the copper content and leave behind other metals" - that is not the way metal is extracted from its ore. I mean you cannot beat an ore to extract metals. The extraction involves one of the various techniques - carbon reduction, thermal reduction, self reduction, electrolysis etc. Since your characters do not have modern metallurgical techniques or equipments, I would suggest carbon reduction as the most suitable method. This is used by the River Valley Civilisations in Egypt, Indus, Mesopotamia etc, 7000 years ago . Some charcoal mixed with these nodules (both powdered and mixed thoroughly) taken in a clay retort and burnt will reduce these nodules.Metal will be separated and, being heavy, will be collected at the base. A search in the web may give you the details of this technique.
I hope this will help. Not for 10 points, but for an author who values accuracy in his fiction.
My very best to you.

Nickel can be extracted through standard processes of pyrometallurgy using carbon-semlting. Actually it is done that way. I am not sure about cobalt and manganese, but since these two metals have been reported in ancient history, there must be some simple technique. Another correction, no bellows - the basic idea is to restrict supply of air, if not stopping it altogether. That is why, the old clay retorts for smelting (I have personally examined them at several places of ancient mining) have very narrow openings.

Unfortunately, I am professionally a geologist and NOT a metallurgist. What you need are facts from both the sources. Only then you can combine them to get to your desired accuracy.