The Farewell Rock is the name given to a series of

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

s at the boundary of the

Coal Measures In lithostratigraphy, the coal measures are the coal-bearing part of the Upper Carboniferous System. In the United Kingdom, the Coal Measures Group consists of the Upper Coal Measures Formation, the Middle Coal Measures Formation and the Lower Coal ...

with the underlying

Marros Group The Marros Group is the name given to a suite of rocks of Namurian age laid down during the Carboniferous Period in South Wales. These rocks were formerly known as the Millstone Grit Series but are now distinguished from the similar but geographi ...

in South

Wales Wales ( cy, Cymru ) is a Countries of the United Kingdom, country that is part of the United Kingdom. It is bordered by England to the Wales–England border, east, the Irish Sea to the north and west, the Celtic Sea to the south west and the ...

. Once thought to be a single sandstone, it is now accepted that the same name has been applied to several different sandstones of similar age across the

South Wales Coalfield The South Wales Coalfield ( cy, Maes glo De Cymru) extends across Pembrokeshire, Carmarthenshire, Swansea, Neath Port Talbot, Bridgend, Rhondda Cynon Taf, Merthyr Tydfil, Caerphilly, Blaenau Gwent and Torfaen. It is rich in coal deposits, espec ...

. The sandstone unit known as the Farewell Rock in the

Pembrokeshire Coalfield The Pembrokeshire Coalfield in West Wales is one of the smallest British coalfields, but continuously worked from the 14th to 20th centuries. The main coalfield extends across south Pembrokeshire from Saundersfoot on Carmarthen Bay westwards to Bro ...

is continuous with the Cumbriense Quartzite of the main South Wales Coalfield. These are assigned to the uppermost part of the Marros Group (the former Millstone Grit Series) which is of

Namurian The Namurian is a stage in the regional stratigraphy of northwest Europe with an age between roughly 326 and 313 Ma (million years ago). It is a subdivision of the Carboniferous system or period and the regional Silesian series. The Namurian is ...

age. In the South Wales Coalfield, the name is given to a thicker, overlying (and hence younger) sandstone unit which, though formerly assigned to the Millstone Grit Series, is now assigned to the Lower Coal Measures which are of Westphalian age. The name is said to have been coined by

ironstone Ironstone is a sedimentary rock, either deposited directly as a ferruginous sediment or created by chemical replacement, that contains a substantial proportion of an iron ore compound from which iron (Fe) can be smelted commercially. Not to be con ...

miners who once worked the

siderite Siderite is a mineral composed of iron(II) carbonate (FeCO3). It takes its name from the Greek word σίδηρος ''sideros,'' "iron". It is a valuable iron mineral, since it is 48% iron and contains no sulfur or phosphorus. Zinc, magnesium and ...

deposits which stratigraphically overlie this

rock unit A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features (facies) that characterize it ...

. Digging beyond i.e. deeper than this bed would yield no further

iron ore Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, or deep purple to rusty red. The iron is usually found in the fo ...

and so, on reaching it, they could bid a 'farewell' to further riches. The name was subsequently adopted by colliers in search of

coal Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen. Coal is formed when dea ...

which occurs in the same Coal Measures

strata In geology and related fields, a stratum ( : strata) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as ei ...

. The Farewell Rock has itself been worked for the production of

refractory In materials science, a refractory material or refractory is a material that is resistant to decomposition by heat, pressure, or chemical attack, and retains strength and form at high temperatures. Refractories are polycrystalline, polyphase, ...

bricks, the high purity of the sandstone (over 98% silica) being suitable for this purpose.Barclay W.J. et al, 1989. Geology of the South Wales Coalfield, Part II, the country around Abergavenny, 3rd edn, Mem. Br. Geol. Surv. sheet 232 (E&W)

References

{{coord, 51.9250, -3.4884, display=title} Carboniferous United Kingdom Geology of Wales