Open questions: Merthyr Tydfil

Where sources disagree, MineArchive keeps both accounts rather than picking one; where a fact could not be settled, the record says so. 21 such claims on 15 records. All regions.

Bedlinog Drift

• Dowlais Collieries Limited started the Bedlinog Drift in 1932. (disputed)

Blaen Rhas Colliery

• A separate account of the wider Dowlais Collieries group describes Blaen Rhas as worked for coal and fireclay, closing in November 1901. (disputed)
• J. Edwards, 28, a collier, died in a roof fall "at Blaen Rhos" on 14 June 1875 — very likely this colliery under a variant spelling. (uncertain)

Buxtons Colliery

• A Dowlais drainage level known as Buxton's, or the Purple Level, carried the ironworks' 'Dowlais pattern' culverts and was still in good condition in the 1960s. (uncertain)

Coly Colliery

• The Dowlais Iron Company's own account of its 1887 closure ties the Colly levels' end to that date, but the more detailed level-by-level record instead places closure of all the levels at 1925, consistent with a separate account of Dowlais's 1924 colliery holdings that no longer names Coly separately. (disputed)

Gethin Colliery

• A second explosion on 20 December 1865, in the Upper pit, killed 34 men and boys. (disputed)
• The 1865 death toll is given as 36 elsewhere. (disputed)

Graig Colliery, Pentrebach

• The Lower Four Feet, the lowest workable seam, lay at 186 yards. (disputed)
• The No.1 Pit worked the Lower Four Feet seam at 142 yards and the No.2 the Nine Feet at 128 yards. (disputed)
• A Graig was recorded in 1837 with a 60-yard shaft and 50 men under W. and R. Thomas; in 1843 a Graig was working steam coal for the Plymouth Iron Company and then Hill's Plymouth Company. (uncertain)

Nantwen Colliery

• One account places closure in 1924 alongside the Bedlinog pits; NMRS's own manpower series instead reports Nantwen jointly with a mine called Danyderi from 1923 through to 1931, implying some working continued past 1924. (disputed)

North Tunnel Colliery

• A pit named simply "Tunnel" is recorded sharing the Lower-Four-Feet, Little/Seven-Feet, Rhas Las/Nine-Feet and Red Vein seams with the wider Dowlais Collieries complex into 1917; very likely the same pit as North Tunnel, though not independently confirmed. (uncertain)

Pant-y-Waun Colliery

• Pant-y-waun Pit, Carno Drift and Mine Pits Nos 1 and 2 were closed about 1886, after which the railway served Tunnel Pit and Fochriw instead. (uncertain)

Penyard Colliery

• One account gives abandonment in 1901; a separate account instead keeps Penyard within the wider Dowlais Collieries group's shared workings (including the Little/Seven-Feet seam, abandoned July 1917) until the whole group's 1924 closure. (disputed)

Penydarren Colliery

• On 2 May 1870 D. Hughes, R. Jones and T. Jones were killed in an explosion. (disputed)
• It ceased production in 1895 but was kept for pumping. (disputed)

Price's Colliery

• A plan of the Dowlais watercourses and levels lists a 'No 2 Thos Prices' level, recording seams from the Two Feet Nine and Four Feet coals to the Rosser ironstone; it may be the same working. (uncertain)

Taff Merthyr Colliery

• Production ceased on 30 October 1992 according to one account, though another gives a final shift as late as 11 June 1993; the winding gear was demolished by controlled explosion on 22 July 1994 after a proposed miners' buyout fell through. (disputed)

Trelewis Drift Mine

• The BGS mine-plans catalogue holds a Mining Remediation Authority abandonment plan titled 'Trelewis' (catalogue SW106, Mynyddislwyn, dated 1950); the catalogue gives no location and the plan's details do not clearly tie it to this working, so it may belong to another of the same name. (uncertain)

Waunwyllt Level

• Robert Thomas took an annual tenancy from the Earl of Plymouth for the opening and mining of a small coal level at Waun Wyllt near Abercanaid; the date is given as 1824 by the Dictionary of National Biography life and as around 1824 by Welsh Coal Mines. (disputed)
• The Northern Mine Research Society and the Heneb historic landscape characterisation both date Robert Thomas's move to Merthyr Tydfil and the opening of the Waunwyllt level to 1828. (disputed)