The Mineral Leadhillite

Leadhillite is a mineral that is a hydroxide of lead carbonate, sulfate and is related to anglesite.  Its chemical formula is Pb4SO4 (CO3) 2 (OH) 2. This mineral uses the monoclinic structure to crystallize, but crystal twinning creates forms that are pseudo-hexagonal. This mineral displays crystals with adamantine luster, translucent to transparent with varying colors. Its Mohs hardness of 2.5 and a density of 6.26 – 6.55 renders its soft mineral.

Chemical Formula  
Pb4 (SO4) (CO3) 2 (OH) 2 

Derivation of Name  
French, from Lead hills, Lanark shire, Scotland + French -it

Crystals are frequently microscopic to small in size, and almost always pseudo-hexagonal, being tabular having a hexagonal outline. Crystals in prismatic form are also found. The simplest form having faces parallel to axis b and cutting axes a and c (represented as {101} may get formed. In such cases it may be curved or striated.

It’s not used as a gemstone.

The said variety occurs in the Susanna Mine at Leadhills, Strathclyde, Scotland, UK.  Leadhillite is a scarce mineral in deposits of oxidized lead. Other than Scotland it is also found in Austria, England, the US, Australia and Namibia among many others. 

Leadhillite is a beautiful mineral having a bright luster. Often, it is found with other rare and attractive, oxide minerals.  The other minerals with which it is often found are highly preferred by collectors. It is very aptly named after the locality where it is found in Leadhills, Lanarkshire, Strathclyde, Scotland.

It gets formed as a secondary mineral in the oxidation region of lead deposits. At times it pseudomorphises other lead minerals while at other times it gets pseudomorphed by other lead minerals. A pseudomorph is a mineral that has changed either the chemistry or structure of an earlier mineral, without altering the outer shape of the original mineral, thereby creating a crystal with the outline of one mineral, but is in fact either chemically and/or structurally a different mineral.

It is colorless or may have sky blue, white, yellow, pale sea green or gray color. Usually, its color fades toward the middle of the crystals.

6.4 ga/cm3

2.5 - 3

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