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Dear Rob I've never worked on ores of this composition, but some of our Glamorgan ores have a slightly elevated Ba content (from barite). This is nowhere near as high as yours, but gets up towards 1% BaO in the bloomery slags (and in blast furnace slags too - but thats not exactly pertinent). In general, bloomeries seem remarkably forgiving/adaptable. I wouldn't have expected the As or Zn to be a particular problem, as most would get burnt off in the stack (except as a problem for the health of the smelters maybe). I understand that the thermal decomposition of barite in air occurs at 1580C and in some of the Glamorgan slags (Roman to Medieval, IA slags not analysed yet) I seem to remember that I *thought* that the barite was being inherited by the slag (it wasn't something I looked at in detail - I could go back to the data to check, if its significant though). I guess a lot of barite passing through the system in this way might cause a problem. This is speculation however - I really don't know about the behaviour of barite in contact with an iron silicate melt. I would get the archaeologists to provide analyses of the slags from the bloomery! Tim On 17 May 2005 at 12:48, Rob Ixer wrote: > Dear All > I have been doing the petrography of spoil and in situ material from an IA > iron mine in the Alps but have been asked to comment on the suitability of > the ore for iron manufacture- there is a smelting site associated with the > mines so they must have been ore. > > Anyway the main mineralogy is very simple, limonite (40 -60wt % Fe2O3) plus > barite (1-16+ wt % BaO) but also 1 -2 wt % ZnO, as > smithsonite/hydrozincite; > <1 wt % Pb as cerussite/galena; > > 0.5 wt % As2O3,(The Gods knows where) a few % silica -no Cao, MnO almost > no MgO. > The ore is a gossan from a zinc-lead sulphide occurrence in dolomitic > carbonates. > > Would the high S be a problem? Or could they beneficiate out the barite- > some of the limonite is pretty free of barite and baryte occurs in thin > veins and knots. Is the As or Zn a problem? > > Any comments would help I only want a short paragraph. Any similar ores > that > you know of worked in the late IA?? > > > Cheers > > Rob. ixer -- Dr Tim Young Email: [log in to unmask] Web: www.geoarch.co.uk Phone: 029 20747480 Mobile: 07802 413704 Fax: 08700 547366