The Denbighshire Coalfield in north-east Wales

Wales

Wales is a country that is part of the United Kingdom and the island of Great Britain, bordered by England to its east and the Atlantic Ocean and Irish Sea to its west. It has a population of three million, and a total area of 20,779 km²...

 is one of the smaller British

Great Britain

Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...

 coalfields. It extends from near Caergwrle

Caergwrle

Caergwrle is a village in the county of Flintshire, in north east Wales. Approximately 5–6 miles from Wrexham and situated on the A541 road, it is contiguous with the village of Abermorddu and closely related to the village of Hope . The village lies on the River Alyn and sits at the base of Hope...

 in the north, southwards through Wrexham

Wrexham

Wrexham is a town in Wales. It is the administrative centre of the wider Wrexham County Borough, and the largest town in North Wales, located in the east of the region. It is situated between the Welsh mountains and the lower Dee Valley close to the border with Cheshire, England...

, Ruabon

Ruabon

Ruabon is a village and community in the county borough of Wrexham in Wales.More than 80% of the population of 2,400 were born in Wales with 13.6% speaking Welsh....

 and Rhosllanerchrugog

Rhosllanerchrugog

Rhosllannerchrugog is a large village and local government community, the lowest tier of local government, part of Wrexham County Borough in Wales.-History:...

 to Chirk

Chirk

Chirk is a small town and local government community, the lowest tier of local government, part of Wrexham County Borough in Wales. It has a population of over 4,000....

 in the south. A small part extends into Shropshire

Shropshire

Shropshire is a county in the West Midlands region of England. For Eurostat purposes, the county is a NUTS 3 region and is one of four counties or unitary districts that comprise the "Shropshire and Staffordshire" NUTS 2 region. It borders Wales to the west...

 around Oswestry

Oswestry

Oswestry is a town and civil parish in Shropshire, England, close to the Welsh border. It is at the junction of the A5, A483, and A495 roads....

. Beyond Caergwrle the coal-bearing strata

Stratum

In geology and related fields, a stratum is a layer of sedimentary rock or soil with internally consistent characteristics that distinguish it from other layers...

 continue northwards as the Flintshire Coalfield

Flintshire Coalfield

The Flintshire Coalfield in north-east Wales is one of the smaller British coalfields. It extends from the Point of Ayr in the north, along the Dee Estuary through Connah's Quay to Caergwrle in the south. A small part extends onto the Wirral i.e. English coast of the estuary at Neston which was the...

; Together the two coalfields are known as the North Wales Coalfield

North Wales Coalfield

The North Wales Coalfield comprises the Flintshire Coalfield in the north and the Denbighshire Coalfield in the south. It extends from Point of Ayr in the north, through the Wrexham area to Oswestry in Shropshire in the south....

. The last deep mine to operate in the coalfield was Bersham

Bersham

Bersham is a small Welsh village in the suburbs of the county borough of Wrexham that lies next to the River Clywedog. Wrexham owes a large amount of its original industrial heritage to Bersham, but despite this the village still retains a rural feeling....

 Colliery which closed in 1986. Prior to this time, as many as 38 collieries had been in operation across the area, with a peak output in excess of 2.6 million tons, and giving employment at the height of production to some 12,000 men.
Several coal seams are named in the sequence. All of the seams occur within the Bettisfield Formation with the exception of the Morlas which occurs in the Coed-yr-Allt Formation. The seams are listed stratigraphically with the uppermost (youngest) at the head of the list and the lowermost (oldest) at the foot.

• Morlas
• Bersham Yard Group; from Alpha (or Alpha Rider) through Beta Rider, Beta and Gamma to Delta (or Delta Bench)
• Upper Stinking
• Warras
• Lower Stinking (known as Brassy at former Moreton Hall Colliery)
• Powell
• Hollin
• Crank
• Quaker
• Main (was known as Six Foot at Quinta Colliery, Bottoms at Preesgwyn Colliery, Bind and Bench at Moreton Hall Colliery and Yard in the Oswestry area)
• Crown
• Upper Red
• Lower Red
• Cannel
• Fireclay Group (includes Stone, Half Yard, Firedamp, Bottom Four Foot and Two Foot seams)
• Nant
• Ruabon Yard
• Premier
• Llwyneinion Half Yard
• Chwarelau

The Smiths seam, which lies between the Main seam and the Lower Stinking seam was known as the Upper Yard at Moreton Hall Colliery and Rover at Oswestry Colliery.