In an area in France that I am studying there is something that puzzles me.
Maybe you can help.
The facts are that high up on the "Gaize", a sort of chalck/sand stone,
there are a couple of dozen pits nicely aligned along an old disused road.
One of these pits was excavated by the archaeological service some 3 years
ago and it turned out to be a bottle-shape shaft of 23 m deep. The shaft
does not reach any other layers, just the gaize, so no flint mine or the
sort. At the bottom of the shaft some roman-age pottery sherds were found.
On these sherds there is a thick (5 mm) layer of glass.
The area is known to be intensively used in the Roman era and there has been
glass-making industry (Roman aged) in that region. 
The stone "Gaize" is very fire-resistant.

The French archaeologists concluded that these shaft relate to this glass
making industry. Problably extracing the chalcky sandstone and using it for
glass-making. This would mean that the glass-ovens could not have been far
from the shafts. I was asked to carry out a survey at the shafts to detect
ovens with a magnetometer. I did two shafts covering an area of 20x25 meters
and 30x50 metres, keeping the shafts in the middle. In these surveyed area's
I found an absolutely silent magnetic area, meaning no ovens of other
burning activities at all. The measurements are so clean, there is not even
a smallest hint of metal. 

Even when I started the survey I told the French archaeologists I did not
beleave these shaft being used for glass-making. These sort of shaft I know
from other regions in France and from Britain (dene-holes), Germany, The
Netherlands and Italy, and they are always chalck-pits. Mostly used to
extract chalck to chalck the fields, but sometimes used as quarries for
building stone. Maybe these shafts were used to extract stones to build
glass-ovens, but that would be the maximum relation. 
The fact that they use pits where they can extract the gaize relatively easy
in open-cast mining to me means nothing as I know many other site where very
labour-intensive shafts were lowered and maybe 500 m away the stuff just
simply surfaces, so obviously other parametres are in place as well, that we
do not know of (yet). 


My question is:
- Does anyone have any knowledge of these chalck-pits relating to
glass-industry? I am convinced they relate to chalck mining or quarrying,
but please convince me of the opposite. 

Best wishes,

Joep Orbons

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