Editorial Feature

Scotlandite - Occurrence, Properties, and Distribution

Aug 15 2013

Image Credit: Hamayun Kabir/Shutterstock.com

Article updated on 06/03/20 by Kerry Taylor-Smith

Chemical Formula – PbSO₃

Scotlandite is a monoclinic-prismatic mineral containing sulfur, oxygen, and lead. The mineral was discovered in 1984 in the Susanna mines of the Leadhills, South Lanarkshire, Scotland. It is named after its place of discovery.

Properties of Scotlandite

The following are the key properties of Scotlandite:

Cell Data

Space Group: P2₁/m
a = 4.505(2)
b = 5.333(2)
c = 6.405(2)
β = 106.24(3)°
Z = 2.

Crystal Data

Monoclinic, meaning the crystals have three axes of unequal length, two being perpendicular to each other
Point Group: 2/m
Crystals are elongated along [001], spear- or chisel-shaped, with {021}, {031}, {100}, {010}, rare {011}, {032}, to 3 mm, in radial and fan-like aggregates
X-ray Powder Pattern: 3.99 (10), 3.25 (8), 3.38 (7), 2.66 (7), 2.56 (5), 2.24 (5), 2.01 (5).

Chemical Composition

Elements	Content 1	Content 2	Content 3
PbO	77.85	79.03	77.70
SO₂	19.88	17.89	22.30
Total	97.73	96.92	100.00

Content 1: Leadhills, Scotland; by electron microprobe, sulfite confirmed by IR and secondary ion mass spectrometry; corresponds to Pb1.06S0.94O2.94.

Content 2: Argentolle mine, France; by electron microprobe, corresponds to Pb1.16S0.91O3.

Content 3: PbSO₃.

Optical Properties

Transparent to translucent
Optical Class: Biaxial (+)
Orientation: Y = b; X ^ a = 15°–20°; Z ^ a = 4°
Dispersion: r«v, strong
α = 1.95–2.035
β = 2.00–2.040
γ = 2.085–2.10
2V(meas.) = ∼35°
2V(calc.) = 37°40'.

Estimated Properties

.	.
Electron density	Bulk density (electron density) = 5.49 g/cm³ note: Specific gravity of Scotlandite = 6.46 g/cm³
Photoelectric	PE_Scotlandite = 1304.34 barns/electron U = PE_Scotlandite x ρElectron density = 7156.98 barns/cm³
Fermion index	Fermion index = 0.16 Boson index = 0.84
Radioactivity	Scotlandite is not radioactive.

How to Identify Scotlandite

Scotlandite is either colorless or occurs in light yellow or a gray-white color. It has perfect cleavage and/or a good, white streak, and an adamantine to resinous luster, appearing pearly on cleavages. It can be formed as prismatic, microscopic or as fan-shaped crystals. The density of scotlandite is 6.37 g/cm³, and its hardness is 2 on the Mohs scale, akin to gypsum.

Global Distribution

Scotlandite is distributed in the following places:

Leadhills, Lanarkshire, Scotland
Roughton Gill, Caldbeck Fells, Cumbria, England
Argentolle mine, near Saint-Prix, Saone-et-Loire, France
Haus Baden mine, near Badenweiler, Black Forest, Germany
Tsumeb, Namibia.

Occurrence of Scotlandite and Useful Mineral Association

Scotlandite occurs as a very rare secondary mineral, formed in the oxidized zone of hydrothermal lead deposits. It is closely related to galena, caledonite, leadhillite, lanarkite, mattheddleite, quartz, pyromorphite, cerussite, macphersonite, susannite, barite, and anglesite.