MATLOCKITE

    Class : Halides
    Subclass : Chlorofluorides
    Crystal system : Tetragonal
    Chemistry : PbFCl
    Rarity : Rare

Matlockite is a secondary chloro-fluoride from the oxidation zone of lead deposits. The necessary supply of chlorine promotes the formation of matlockite in salty, evaporitic or marine environments. It is therefore found in millimeter-sized crystals in seaside slags. It owes its name to where it was discovered : the Bage mine near Matlock (England). Matlockite forms flattened tabular to lamellar crystals, sometimes squat pyramidal, gathered in rosettes, in radiated subparallel or hemispherical aggregates. It is colorless or pale yellow to yellow-orange, sometimes orange-brown.

Main photo : Matlockite from Cromford, Derbyshire, England © Ru Smith

2 cm matlockite from Cromford, Derbyshire, England © Rock Currier
Matlockite from Waterbank Mine, Ecton, England © Steve Rust
Matlockite from Lavrion, Greece © Christophe Boutry
Matlockite from Cromford, Derbyshire, England © Uwe Haubenreisser

Matlockite in the World

The largest crystals measure 5 cm and come from the definition locality : the Bage and Wallclose mines, near Matlock (Derbyshire, England). Interesting samples have been discovered in the oxidation zones of numerous other polymetallic mines, associated with other secondary lead minerals (leadhillite, cerussite, sometimes diaboleite, etc...); among the most significant include Apache (Arizona), Challocollo (Chile) and especially Mammoth St-Anthony (Arizona) which supplied 8 cm cleaving blades.

Matlockite in France

In France, matlockite is present in the St-Lucie vein in Lozère.

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 2.5 to 3
Density : 7.12
Fracture : Irregular to sub-conchoidal
Streak : White to gray

TP : Transparent
RI : 2.040 to 2.150
Birefringence : 0.110
Optical character : Uniaxial -
Pleochroism : None
Fluorescence : None

Solubility : Nitric acid

Magnetism : NoneRadioactivity : None