Fluorite from Blackdene Mine Collectors Guide

Blackdene mine was acquired by the United Steel Companies Ltd., in 1949, they started a vigorous campaign of exploration and development. By 1951 two of the sumps had been pumped and cleared, and by 1954 most of the mine had been cleared and investigated. Some production was achieved from the old stopes, but it was concluded that the best prospects lay within the virgin ground below the Blackdene level. Four new levels where started below the Blackdene level at 12, 29, 44 and 58 meters. These were accessed from vertical shafts and 4 inclines, these new levels accessed beds from the three Yard Limestone down to the alternating beds below the Scar limestone. The beds in this area contained less shale than typical for the area this resulted in the ore shoot being longer than usual at 853meters this almost reached the Slitt vein. This Ore shoot was considered worked out by 1973 apart from the ground left to support the Blackdene level.

To access further reserves, a new incline and haulage way was driven from surface. Blackdene vein was cut at 8.8 meters below the 58m level, below the single post limestone. The vein at this point was seen to be deteriorating with one small section of workable ground found. The main purpose of this new incline was to access the Slitt vein. An attempt to work the Blackdene vein in the Whin Sill was also made from the No.3 incline. This proved to be unsuccessful as the vein proved to be only 0.3 meters wide. The Whin Sill is unusually thick at this point being 87.8m thick, this maybe due to the Sill being inclined as it changes horizon.

The Silverdykes vein was considered to be an extension of the Blackdene vein on the other side of the Slitt vein. Dunham points out this is unlikely as these veins dip in opposite direction making them being related unlikely. The Silverdykes vein was worked from the Silverdykes Level (NY 8794 3946) in the Pattinson Sill, parts of the vein where also worked from the Blackdene level via sumps into the Silverdykes level. This area of the Blackdene mine was not reopened by the United Steel Co., ltd.

In 1962 with the development work being at an advanced stage on the Blackdene vein, it was decided to drill the Slitt vein from the Ridleys Crosscut. A series of low angle boreholes interested the Slitt vein in the Six Fathom Hazel, this showed encouraging widths of Fluorspar. Levels where driven to the Slitt vein by the United Steel Co., Ltd. From the 29m level (Below the Blackdene level), a further level was driven later from the 58m level. These levels encountered an ore shoot 304x52m with widths up to 4.2m but usually averaging 1.7m, This ore shoot was extracted by 1972. Development work below this ore shoot showed the vein was mainly Ankerite. The company referred to this ore shoot as the North Slitt, with the ground being located to the west of the Blackdene vein. Further attempts where made to test the Slitt vein to the East of the Blackdene vein. In the easternly direction good ground was found on the Slitt vein from the 12m level in the Six Fathom Hazel, this ore continued for only 76m. After this disturbed ground was driven through for 175m where good ground was again entered. In this section of the mine ore shoots where developed in the Scar Limestone and continued for 692m with an average width of 1.66m.

The united Steel Companies Ltd., was nationalised in 1967 along with many other companies to Form British Steel. The mine passed to British Steel in 1967 and became there primary source of Fluorspar for flux. With the collapse of the steel industry in the early 1980s the mine was sold to Minworth Ltd. By 1986 the deeper levels on the Slitt vein showed impoverishment. The mine was placed on care and maintenance with the pumps being turned off in 1987 and the site cleared. As a Fluorspar mine the recorded production was 370,237 tons of Fluorspar with 4,500 tons of lead in addition to the circa 15,000 at least produced prior to this period making the minimum amount of lead produced probably around 20,000 tons.

Collector's Guide

Blackdene is well known amongst collectors of English Fluorites for producing some of the finest purple Fluorites in the Weardale area. The mine is rightfully famous for producing some of the best elongated Fluorite crystals, competing with Boltsburn mine when it comes to the quality of these elongated specimens. While purple might be the most common colour for the Fluorites from Blackdene the silverdykes vein did produce some straw yellow examples.

Often the best Fluorites from Blackdene are associated with a combination of minerals usually Galena and Chalcopyrite. The combinations of deep purple Fluorites with bright metallic often modified Galena crystals are often highly sort after, as are the combinations with bright brassey Chalcopyrite crystals. As with most mines in the Weardale valley the gummiest Fluorites are often smaller in size with the crystals losing their clarity as they increase in size.

Notable Finds

Significant finds of both Fluorite and Galena specimens where found while the new incline was being sunk below the horse level when British Steel worked the mine.