Dear Alasdair
I'm actually doing some work on gossan iron ores from that area at present.
Its not exactly the information you are after, but I'm writing up a late Iron
Age iron smelting site on the west of Truro. The site lies adjacent to shafts
associated with East Wheal Falmouth, but the site gives ample evidence for
the smelting of gossan for iron around 2000 yrs ago. The work includes
some geochemical and microstructural work on the gossan samples found
stored (or hidden) in one of the Iron Age houses, as well as on the
archaeometallurgical residues. It should be published shortly by the
Cornwall Archaeology Unit.
I assume that the sort of layered or boxstone textures I am seeing is what
the mineral statistics would have called gossan - with perhaps this being on
the verge of what they might have called iron ore (it is locally quite dense). I
would imagine the ochre would have been very soft iron ore, with umber the
manganese oxide dominated equivalent. The material I have shows voids
filled with late stage Mn oxides (umber). At an earlier stage in this project I
tried to locate gossan specimens from the area in various collections - in an
attempt to work out how the term was used and to get comparative
analytical data, but that effort unfortunately failed to track down any
contemporary material.
Best wishes
Tim
On 30 Jan 2008 at 9:31, Alasdair Neill wrote:
> In updating the "Cornish Mines" volume originally published by Exeter
> University, we are adding data from the Mineral Statistics omitted in
> the original edition. This includes data for "gossan" which was
> produced by mines particularly in the Wheal Jane area.
> The geological meaning for gossan is of course well known (the
> ferruginous weathered capping typically found in association with
> sulphide mineralisation), but can anyone say what it was used for
> commercially? There are references to attempts to extract gold from
> gossans in that area in the early 1850's gold boom, but it seems
> unlikely this ever led to anything.
> The Mineral Statistics data lists it seperately from ochre, umber,
> &
> iron ore which may have had similar uses.
>
> Alasdair Neill.
--
Dr Tim Young
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Web: www.geoarch.co.uk
Phone: 07802 413704
Fax: 08700 547366
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