Banc Tynddol Roman and Early Medieval Lead smelting [SN 809 748]
When John Leland, the King’s Antiquary under Henry VIII, passed through the Ystwyth
Valley sometime between 1536 and 1539 as part of his survey of the monastic lands
of the nearby Strata Florida Abbey he referred to the mining on this hill and Graig
Fawr (to the west) and to the evidence for former lead smelting in the vicinity.
The geologist O.T.Jones in 1921 noted the traces of smelting debris at Penguelan
in the valley bottom, and this site was then re-discovered in 1990 following survey
work by the EMRG.
Excavations carried out in 1999 and again in 2002 and 2003 revealed the destroyed
and strewn remnants of at least three Early Medieval wind-powered bole furnaces dating
to two distinct periods: 880 -1020 yrs cal AD and 1030-1300 yrs cal AD. The latter
phase at least might relate to the working of the mine by the lay brothers or tenants
of the Cistercian monks of Strata Florida. These hearths appear to have been built
as simple stone structures above ground and the smelting process seemed quite inefficient.
A geophysical magnetic susceptibility survey carried out in 2002 suggested the existence
of another type of furnace (PSS4) which on excavation proved to be a clay and stone-lined
pit bole hearth of Roman origin.
This hearth seems to have been used several different times was worked in a quite
different way. This produced a lead-poor glassy slag and a pool of metal which on
occasion had overflowed and solidified in a channel of lead, the course of which
could be traced some 8m downslope. A radiocarbon date obtained from charcoal closely
associated with this lead suggested that the smelting furnace was in use during the
Roman period sometime during the 1st-2nd. Century AD (Timberlake 2002).