Sampling Blooms from Austria

Today I sampled some bloom pieces that make up part of a small set of debris sent to me by Brigitte Cech, an independant archaeological researcher working on the Ferrum Noricum sites.

Brigitte was pretty sure this was likely to be a Roman site, so she had a look using a metal detector and a little bit of sampling excavation, and pulled out some ore, three blooms, slag fragments and furnace lining (amongst other stuff!). I’ve mentioned this stuff before, as I was pretty excited about working on it.

Today I cut off some small pieces from the three blooms. Blooms are the accumulated iron that is produced in the furance – they’re called blooms due to their ‘spongy’ appearance and the way they build up over time. Essentially they look like nasty pieces of corroded rock. They’re heavier than rock though, but that’s a bit hard to spot if they’re not too big and not too small. However if you cut them open, you get to see something a lot more exciting. Basically the whole nasty lump is made of shining bright iron!

To put that in perspective, that iron was smelted sixteen hundred to two thousand years ago. It’s lain in the ground for all that time, and look how little rust there is! I’m told that it’s pretty rare for an archaeological bloom to look like that – most are just massive lumps of rust with a core of metal surviving. My friendly lab technician asked me if it was material from a modern experimental smelt! But Brigitte tells me that they have pottery and brooches from the site that date it securely to the Roman period, so the lack of corrossion is very notable.

It makes me think that there’s something else in the iron here that’s inhibiting the corrosion. Unfortunately the analyses are going to have to wait until the mid-end of May, but I’m sure I read something somewhere about something special in the Ferrum Noricum ores. I’m currently waiting for Brigitte’s book (see below)- it’s still being catalogued by the library – but I suspect there’ll be something like that going on.

Reference:

Die Produktion von Ferrum Noricum am Hüttenberger Erzberg : die Ergebnisse der interdisziplinären Forschungen auf der Fundstelle Semlach/Eisner in den Jahren 2003-2005 = The production of Ferrum Noricum at the Hüttenberger Erzberg : the results of interdisciplinary research at Semlach/Eisner between 2003-2005
Brigitte Cech (Hrsg.) Wien : Österreichische Gesellschaft für Archäologie, 2008.

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