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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
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).
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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).
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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).
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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).
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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).
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