Just been reading an account of these mines, in Monmouthshire, in Cwbran Caving Club Journal 16. I'd never heard of them before. Unusual geologically in that they are in Silurian limestones. The only historical information given is that there were iron works in the area in the 16th C. Anyone got any further info or been there?

Not previously heard of this mine either. Glascoed is annoyingly on the edge of 1" BGS sheets 232 and 249. The Usk Anticline brings Ludlow and Wenlock Beds to surface.

Does the Cwmbran CC Journal article give a location more exact than just 'Glascoed', and a geological location more exact than just in Silurian limestones?

There are a number of Silurian limestones to choose from: Trostrey Lmst and Usk Lmst, both top Wenlock; Upper Bringewood Beds / Aymestry Lmst / Lower Llanbadoc Beds, which are high/top Grotsian = mid Ludlow; the occasional lmsts of the underlying and laterally equivalent Lower Llanbadoc / Upper Forest Beds which are high Grotsian = mid to high Ludlow; the occasional lmsts of the Upper Llanbadoc Beds which are low Ludfordian = high Ludlow.

As the Glascoed area was massively developed as a WW2 Royal Odnance Factory, surface remains may well have disappeared.

Nothing in T.M.Thomas 'The Mineral Wealth of Wales and its Exploitation' (Edinburgh, 1961) which usually lists every mineral occurrence of the least note. Have you checked the BGS sheet memoirs?

This is intriging - both geologically and because it might have been a source of ore for the otherwise oddly located Monkswood Furnace and Forge (approx ST 33 02) which were built in 1564. References to the furnace and the two forges cease in 1597 but there are indications of a brief circa mid C18 revival of the furnace that - see P.Riden 'A Gazetteer of Charcoal-fired Blast Furnaces in Great Britain in use since 1660' (Cardiff, 2nd ed, 1993), pp.25-6.

Do post if you find additional information or a more exact location.

There is a description of Aberdare No. 1 Level iron mine, Pontypool at ST276991 in Welsh Mines Society Newsletter 61 p. 33 http://www.hendrecoed.org.uk/wms/newsletter/61.pdf .

I'm also aware of the The Wainfelin and Tranch Iron Mine at SO275017.

Dave

The sites are a SSSI (because of their location in the Usk Limestone which is thought to have unusual stratigraphic relations with the other Silurian limestones) and as NE probably are not that keen on widly publicising SSSI locations I won't give a grid ref here. This is because in the past "undesirables" have been known to plunder SSSI sites once their location has become known. The article however includes a copy of the SSSI notification & map. I imagine it should be available in any of the caving club libraries in South Wales.
The Tranch & probably the Aberdare sites are all Coal Measures sites & so would have no connection to these.

The information I've got on this area is certainly not very scientific and is in part very old but it might be of some use to you. About 50 years ago when I was in my early teens I visited some mines with somes friends and equipped with a couple of cycle lamps we went into one of the adits. It was quite spacious with a lot of roof material on the floor. Unfortunately because we left our bikes outside we were spotted by a local resident and told in no uncertain terms told to leave. There are a number of adits in a low escarpment on the lefthand side of the road which takes you down to the local church from the road through the village.
Also about 10 years ago I spotted a couple of small quarries on an OS map and very close to the village. One was very overgrown but there were two spacious chambers leading off the pit. The smaller of the two had a tunnel leading off it but was threequarters filled with spoil. This tunnel was leading in direction of the second quarry but investigating it could not be found. It should have been in a field so I guess it had been filled in by the farmer.
Finally there used to be an adit in the back garden of a house in the village - don't know if its still open.

Davel pm'd me to query the NGR of Monkswood Furnace and Forges. It should be SO 33 02; Riden is in error. (Thanks Davel)

Had a look at the BGS sheet memoirs today. Nothing pertinent in Abergavenny (Sheet 232) 2nd ed, 1927. However, in Newport (249), 2nd ed, 1909, it states on p.6:

"Of the Wenlock Limestone there are four distinct outcrops - namely, at Glascoed, at Common Coed-y-paen, south of Cilfigan Park, and at Dowlais [not the Merthyr Tydfil location of that name - GF] ... The limestone was formerly burnt for lime, but is now [i.e. shortly prior to 1899, date of pub. of the 1st ed - GF] used chiefly for road-metal. It was followed underground north of Glascoed, and the old workings form a line of picturesque caves, the roof of which is formed by about 10 or 11 ft. of mudstone more or less crowded with nodules of limestone, while the rock in requistion was a pure and massive limestone with a thickness of 9 or 10 ft. The workings [in the sense used by the BGS this indicates both surface and underground - GF] cease on the north side of Pentre-waun Wood [the northern part of Pentre-waun Wood and a long length of Wenlock Lmst outcrop to the north were drowned to create Llandefydd Reservoir later in C20 - GF], and for 900 yards there is nothing to indicate any outcrop of limestone, but at Pentre-waun, the pits [i.e. surface workings - GF] recommence...".

In the " List of fossils from the Silurian Rocks of the Usk and Llanfrechfa Inliers" on pp.8-12, there appears locality no.40 "Ty Newydd (Tynewydd, underground quarries near the church at Ton)". I cannot locate Tynewydd or Ton on the OS 1:50,000 map.

I wonder if 'Glascoed iron mines' are synonymous with these underground workings for limestone? How are they described in the Cwmbran CC journal?

I'm no expert but the workings I've seen in the area certainly look like limestone workings with the exception of the entrance in a private garden which is much smaller and could be iron.

The description is that they were "iron mines" & goes on to say "I believe these mines were valued for their limestone as well as the iron content which Bill Gascoine assures me is quite high
"The mines were usually cut into an escarpment and then run parallel with the escarpment face with openings in several places to allow light in. The roof is supported by pillars of rock left standing in strategic positions".

Thanks for this clarification Alasdair. The description accords with the workings described by Geraldus and the location of both accords with the limestone mines descibed by the BGS.

It would appear that the sole authority for an economically viable iron content to these beds is Bill Gascoigne, a college lecturer in chemistry and noted hydrologist and exponent of dye tracing in the caves of south Wales. The Glascoed limestone outcrop does not feature in his most notable summary publication 'The Hydrology of the limestone outcrop north of the Coalfield', pp.40-55 in T.D.Ford (ed.) 'Limestones and Caves of South Wales', Cambridge, 1989.

It is difficult to reconcile the reported assertion of Gascoigne of a 'quite high' iron content with the BGS's analysis of this limestone bed slightly further south at Common Coed-y-Paen, which found only 1.56% FeCO3 and 0.41% Fe2O3 (88.89% was CaCO3) - Newport (Sheet 249) sheet memoir, 2nd ed, 1909, p.7. Additionally, the BGS memoirs of this period were generally very attentative to economic geology and tended to note, albeit very briefly, formerly worked minerals. Nowhere does the memoir mention iron in, or worked in the Wenlock Limestone of the Usk Inlier, nor does the Abergavenny (Sheet 232) memoir which covers the area of the inlier to the north.

I would suggest that either Gascoigne was mistaken, or that he was misreported, and that the Glascoed workings are unlikely to have exploited iron in the Wenlock Limestone.

Incidentally, Ton, which I could not locate on the 1:50,000 OS map, is adjacent to Ton Church which is at NGR SO 331 020, on the northern side of Glascoed village; Tynewydd and some of the underground quarries are presumably adjacent.

I would go along that it was a misinterpretation unless shown otherwise. Nevertheless its still interesting that there were underground workings for Silurian limestone in Wales - of course there were a lot in the Dudley area.