Whitespots-Conlig mines (Whitespots-Conlig vein), Conlig, County Down, Northern Ireland, UKi

Regional Level Types
Whitespots-Conlig mines (Whitespots-Conlig vein)	Vein
Conlig	Village
County Down	County
Northern Ireland	Constituent Country
UK	Country

The Whitespots - Conlig lead mines is an extensive site comprising several spoil heaps, tailings impoundments, capped mine shafts and architectural features including engine houses and chimney stacks. The spoil material contains hydrothermal vein minerals, notably galena, chalcopyrite, barite, dolomite, calcite and rare harmotome (the only known occurrence in Northern Ireland) and ore textures that demonstrate the origin of the mineralization. Museum-quality crystalline specimens of these minerals have been recovered from the site during the past 15 years, and there are many specimens from the site in the Ulster Museum collections.

The Whitespots - Conlig site is situated between c.1.5 and 3km north of the town of Newtownards. A comprehensive account of the history of mining in the area is given by Woodrow (1978). The site straddles sheets 29 and 37 of the Geological Survey of Northern Ireland. The memoir that accompanies sheet 29 gives a detailed summary of the geology and mining history (Griffith and Wilson, 1982). Sheet 37 was published in 1986 and the accompanying memoir (Smith et al., 1991) contains an old photograph of the mine area and a brief review of its economic geology. Three photographs taken in the 1940s and descriptions of the site are included in a book by Kirkpatrick (1998?).

Extensive working of lead ore took place in this area in the early nineteenth century, when up to 15,000 tons of refined lead (and lesser copper and silver) were extracted from ore removed via several shafts. Production declined after 1854 and the mines had closed by 1900 (Woodrow, 1978). The lead vein (not now exposed) trends N6°W and dips at 75°W (Griffith and Wilson, 1982), and is associated with a 'crush breccia' within Silurian greywackes and shales. During the 19th century the vein was mined over a length of 1.6km and to a depth of 366m, with access through 10 shafts and adits. The trend of the lode is marked by a north-south topographic depression or an east-facing escarpment.

The mineralization occurs in silica- and dolomite-cemented breccias and vein-fills. Most of the economic ore material appears to have been in vuggy dolomite-cemented breccias and in barite veins. Sulphides present are galena, chalcopyrite, pyrite, and ferroan sphalerite. The gangue minerals are chalcedony, quartz, dolomite, calcite and barite. Secondary weathering products include cerussite, hydrozincite, bornite, malachite, azurite and limonite. Pyromorphite has been reported but was not observed in this study.

The most abundant hydrothermal mineral is dolomite, which varies from yellow-beige to pink to cream in colour and forms sugary to coarsely crystalline aggregates incorporating angular fragments of country rock, and saddle-shaped crystals in vuggy cavities. Barite is also an abundant gangue mineral, forming white, platy aggregates and occasionally well-developed colourless crystals. Calcite is common as a late cavity- or vein-fill, in both silica- and dolomite-matrix breccias. Calcite occurs as flattened rhombohedra, 'nail-head spar', equant crystals with pentagonal faces and barrel-shaped crystals.

Galena and chalcopyrite are the principal metallic minerals with minor ferroan sphalerite and pyrite. Galena occurs as crystalline masses within the dolomite-matrix breccia and occasionally as well-formed cubic crystals in vugs. Sphalerite forms dark brown, 2-10mm crystals usually enclosed within barite. Chalcopyrite typically occurs as well-formed 2-8mm crystals perched on saddle dolomite.

Of particular interest is the occurrence, in very small amounts, of the barium zeolite mineral harmotome, (Ba,K)1-2(Si,Al)8O16.6H2O. It typically forms transparent, perfectly developed, cruxiform twinned crystals, up to 0.3mm in width and 2mm in length. Harmotome occurs late in the paragenetic sequence and its crystallization is associated with a dolerite dyke of probable Palaeocene (Tertiary) age which intruded through the older breccia and vein mineralization (Moles and Nawaz, 1996). This occurrence of harmotome is the first recorded for this mineral in Northern Ireland. A brief mention by Tschernich (1992, p.242) originates from information supplied by one of us (RN).

The Whitespots - Conlig mine was one of the largest underground mines in Ireland in its heyday. Many features of the mining activity remain, and specimens of galena and other minerals are readily obtained. The site is the only occurrence in Northern Ireland of the unusual barium zeolite, harmotome (Moles and Nawaz, 1996). Since 1994, the site has been used regularly for field visits by students undertaking project work in connection with the MSc course in Applied Environmental Sciences at Queen’s University Belfast. In May 1997, the Mining Heritage Society of Ireland lead a field visit to the Lead Mines and members of the society urged one of us (NM) to become active in conserving and promoting the site. We feel strongly that action is required to conserve features of the site, which includes buildings in various states of dereliction, and to promote interest in the significance of these features to a wider public.