Scotlandite

scotlandite

lanarkite

leadhillite

mattheddleite

Images

Formula: Pb(S4+O3)
Anhydrous sulphite of lead
Crystal System: Monoclinic
Specific gravity: 6.37 measured, 6.40 calculated
Hardness: 2
Colour: Pale yellow, greyish white, colourless, white
Luminescence: Fluoresces yellow under long wave UV
Environments

Hydrothermal environments

Scotlandite is a very rare secondary mineral, formed in the oxidised zone of hydrothermal lead deposits (HOM).

Localities

At the Argentolle Mine, L'Argentolle, Saint-Prix, Autun, Saône-et-Loire, Bourgogne-Franche-Comté, France, scotlandite is associated with leadhillite, susannite, macphersonite, cerussite, pyromorphite, galena and quartz (HOM).

At Short Grain, Deer Hills, Caldbeck, Allerdale, Cumbria, England, UK, scotlandite is not uncommon in blocks of veinstone on the dump. It occurs with anglesite, leadhillite, mattheddleite and susannite, on or closely associated with corroded galena, in quartz and baryte. Crystals range up to about 2 mm in length but are usually between 0.3 and 0.5 mm. They are often white and opaque, and pseudomorphous replacement by anglesite and cerussite is quite common (JRS 9.86).

At Clints Gill (Roughton South Vein), Roughton Gill, Caldbeck, Allerdale, Cumbria, England, UK, scotlandite specimens were collected from an exposed stringer of galena. Pyromorphite, cerussite, malachite and chrysocolla were present in crystalline crusts surrounding the vein. The less oxidised interior contained lanarkite, anglesite, leadhillite, susannite, caledonite, mattheddleite and, rarely, scotlandite. The scotlandite was found in cavities as translucent pale brown pointed crystals, exceptionally to 0.6 mm long, associated with leadhillite and lanarkite. A recent (in 2006) resurvey of the area revealed that flooding had removed about 1.5 m of scree and the locality had been obliterated (JRS 9.86).

At Dry Smale Gill, Roughton Gill, Caldbeck, Allerdale, Cumbria, England, UK, quartz veinstone with a little white laminar baryte is present on the dump. The vein appears to have been almost completely devoid of base metal mineralisation and only a trace of yellow pyromorphite is present on most specimens. A few blocks containing traces of oxidised galena with supergene minerals including minute crystals of scotlandite were found. The scotlandite occurs with leadhillite and mattheddleite in cavities and thin fractures in the centre of poorly mineralised veinstone blocks, sometimes with partly corroded galena. It is the first supergene mineral to have formed (JRS 9.86).
Image

At Higher Roughton Gill, Roughton Gill, Caldbeck, Allerdale, Cumbria, England, UK, scotlandite was found in situ at an exposure on the eastern flank of Balliwag Rigg. It occurs as subtranslucent to transparent pointed crystals which tend to form radiating clusters, and as individual chisel-shaped blades, exceptionally to 0.6 mm in size. The crystals are white, inclining towards grey, brown or colourless, with a distinct resinous lustre. Scotlandite occurs in cavities in highly oxidised galena, where it is commonly associated with caledonite, lanarkite, leadhillite and mattheddleite (MM 53.653).

At Red Gill Mine, Roughton Gill, Caldbeck, Allerdale, Cumbria, England, UK, scotlandite occurs as minute thin prismatic crystals, less than 0.3 mm in size, in cavities in quartz veinstone with a trace of galena, elongated prismatic mattheddleite and blocky leadhillite (JRS 9.86).

At Whitwell Quarry, Hodthorpe and Belph, Bolsover District, Derbyshire, England, UK, a variety of lead-bearing supergene minerals, including scotlandite, was found. The scotlandite occurs as honey brown, white or colourless translucent crystals up to 2.5 mm in length. At Whitwell quarry, scotlandite is associated with bladed lanarkite crystals up to 5 mm in length and euhedral blocky leadhillite. One specimen shows crystals in etch pits in corroded, but fairly bright, galena (JRS 9.87).
In the carbonate-rich limestone environment, scotlandite occurs only in the centre of galena blocks, well removed from the wallrock. Leadhillite apparently forms in similar conditions to scotlandite, and leadhillite crystallises on scotlandite in several specimens from the quarry (JRS 9.88-89).

At Cove Vein and New Cove Vein, Whytes Cleuch, Wanlockhead, Dumfries and Galloway, Scotland, UK, scotlandite was identified as abundant, tightly packed, up-standing crystals up to 0.3 mm in length associated with leadhillite plates and susannite rhombs in a cleft in quartz-galena veinstone. The dumps comprise Ordovician (485.4 to 443.8 million years ago) graywackes with much calcite- and hematite- rich quartz veinstone. Chrysocolla- stained veinstone is locally abundant but lead minerals are generally rare.
Scotlandite crystals up to 0.3 mm in length occur in cavities in quartz with a little residual galena, mattheddleite and anglesite (JRS 9.85).

At the Broadlaw Vein, Broad Law, Leadhills, South Lanarkshire, Scotland, UK, the dumps consist largely of Ordovician (485.4 to 443.8 million years ago) graywackes with quartz veinstone carrying a little laminar white baryte, residual sphalerite and galena.
Scotlandite occurs as small sprays up to about 0.7 mm in length, associated with residual galena and susannite in blocks of massive hemimorphite with minor pyromorphite and wulfenite (JRS 9.85).

At Horner's Vein, Leadhills, South Lanarkshire, Scotland, UK, dumps surrounding a shaft believed to be on Horner's vein contain slightly bleached and altered Ordovician (485.4 to 443.8 million years ago) graywackes with quartz, laminar white baryte, galena and sphalerite veinstone. They have produced numerous specimens of scotlandite. Other rare minerals including lanarkite, susannite, leadhillite, caledonite, chenite and queitite have been identified in cavities in galena and between the galena and cerussite-pyromorphite oxidation rinds.
The scotlandite occurs as translucent pale brown slightly flattened crystals, up to about 0.2 mm long, associated with mattheddleite, leadhillite and, rarely, caledonite (JRS 9.85).
Image

At the type locality, the Susanna Mine, Leadhills, South Lanarkshire, Scotland, UK, scotlandite occurs as chisel-shaped or bladed crystals with a tendency to form radiating clusters. The crystals are pale yellow to greyish white and colourless, sometimes transparent, with an adamantine lustre.
Scotlandite occurs in cavities in massive baryte and anglesite, and is closely associated with lanarkite and susannite; it represents the latest phase in the crystallisation sequence of the associated secondary lead minerals (MM 48.283-288).
Image

At the Lady Anne Hopetoun shaft, Wanlock Dod, Leadhills, South Lanarkshire, Scotland, UK, most of the dumps around the shaft are composed of heavily altered and brecciated graywackes veined by ankerite or dolomite that carries small amounts of quartz, calcite, chalcopyrite, sphalerite, galena and aragonite. Many of these minerals occur in drusy cavities in the carbonates. At one end, the dump contains a small proportion of finer debris that contains considerable amounts of laminar white baryte, galena with cerussite, and highly cellular quartz. These minerals are commonly encrusted either in pale grey-green pyromorphite or in white lead-rich apatite.
Scotlandite occurs associated with anglesite, lanarkite, leadhillite and susannite on galena in fractures or cavities in the kernels of pyromorphite encrusted galena-cerussite veinstone (JRS 9.85).
Image

Formation of Scotlandite

The oxidation of sulphides, anion S2- to sulphates, anion (S6+O4)2- is rather complicated and does not proceed in a single step. Several transient, easily oxidised, intermediate anions are involved and of these thiosulphate (S6+O3S2-)2- and sulphite (S4+O3)2- anions are likely to be the most stable.
Scotlandite Pb2+(S4+O3)2- has been found in close proximity to oxidising galena Pb2+S2- in a number of localities.
Where there is a relatively high concentration of sulphuric acid H2(S6+O4)2-, scotlandite is likely to be unstable with respect to anglesite Pb2+(S6+O4)2-.
At a near neutral pH and above (more alkaline), the carbonate ion (CO3)2- activity (effective concentration) would be expected to render scotlandite unstable with respect to lead carbonate minerals such as leadhillite, hydrocerussite and possibly cerussite; this is borne out by the persistent association of scotlandite with leadhillite and lanarkite, both of which are stable at low carbonate ion activities (concentrations).
Scotlandite typically occurs as a transient supergene species in association with partly oxidised galena in low carbonate environments. The crystals are normally small and inconspicuous and are very easily overlooked (JRS 9.88-89).

Back to Minerals