Geology and Resources

Black Diamond’s resource is 973Mt of high rank anthracite across 3 licence areas, the anthracite has wide domestic and industrial use throughout the United Kingdom and Europe given its high carbon content and calorific value. The anthracite resource can be readily exploited, as the working licences and infrastructure are already in place. Black Diamond is well placed to become the only producer of anthracite in Europe by 2018.

Coal has been produced from the South Wales Coalfield since the mid-1800s. In 1855, the output of the South Wales Coalfield was approximately 8.5 million tonnes per annum. By 1913 it had reached its production peak of approximately 57 million tonnes per annum from around 620 coal mines employing 232,000 men.

Black Diamond is served by two 1200 metre long access drifts originally driven by Unity for the purpose of developing the Six Feet Seam and ultimately the Nine Feet Seam. The Peacock and Caerau Seams are readily accessible. The seams form part of the Middle Coal Measures of the Carboniferous period of the South Wales Coalfield.



Within the Glyncastle licence, the mined anthracite seams are as follows:-

  • Six Feet seam which is a thick, composite seam consisting of HG that splits westwards beyond the area of the licences. Historically, the ‘typical’ section recorded at the neighbouring mines was 2.4m and 2.7m. A seam thickness of 2.2m is taken as a typical section at Black Diamond, although a seam thickness of 2.4m has been recorded during production.
  • Nine Feet seam is a thick, composite seam of HG. The combined Nine Feet seam is recorded to be 1.98m thick at Blaengwrach and 2.13m at Glyncorrwg. The seam has been recorded at a thickness of up to 3.77m at Black Diamond;
  • Peacock seam was mined successfully at Glyncastle in the past, the seam is typically a single leaf of clean coal some 0.91m thick UHG. The seam generally tends to have a moderately silty roof and sandy seatearth floor and has tended to be mined, despite its thickness, as a result of good mining conditions and the high quality of the anthracite.



The coals of the area are folded into broad anticlines and synclines trending east-northeast, intersected by faulting trending at northwest, east-west and northeast-southwest. Gradients in the seam vary, averaging 1:7 over most of the area, steepening to 1:1 in the northernmost part of the licence in the area of the Neath Disturbance.

The area of the licence is marked by the north western development of Neath Disturbance. This trends north east to south west and is related to an ancient Caledonian crustal feature, active throughout the Carboniferous period and in more recent times. In the south of the licence where the bulk of the coal resource is present, the rocks are folded into a gentle east–west trending syncline. This is confirmed by adjacent mine workings.




Historically, in the operations at and adajacent to the old mine, 60 to 80% of the anthracite has been extracted. It is proposed that in short wall mining, a recovery factor of 65% should be considered, the assessed reserves only assume 60%.

The resource in the license area to be intially worked is assessed at 138Mt with 38Mt in the Six Feet Seam, 59Mt in the Nine Feet Seamd and 15Mt in the Peacock Seam.




The reserves in the license area to be intially worked are assessed at 40Mt with 19Mt in the Six Feet Seam and 21Mt in the Nine Feet Seam. in addition the reserves in the Peacock seam are assessed at 9Mt.