Formula: Pb4(SO4)(CO3)2(OH)2
Compound carbonate
Polymorph of susannite and macphersonite
Hardness: 2½ to 3
Streak: White
Colour: Colourless to white, grey, yellowish, pale green to blue; colourless in transmitted light
Solubility: Soluble in nitric acid with effervescence, rendering a residue of lead sulphate. Exfoliates in hot water.

Hydrothermal environments

Leadhillite is common only in deposits that contain very little carbonate mineralisation. Several localities in the Caldbeck Fells, Cumbria, England, and the Leadhills/Wanlockhead mining field, Scotland, meet this requirement, which is why leadhillite is relatively common there. It is quite rare in the nearby carbonate-rich Pennines (JRS 18.10).
For carbonate concentration slightly lower than atmospheric, cerussite and hydrocerussite can co-exist in alkaline environments, with leadhillite in more acid environments, and anglesite in yet more acid environments. At extremely low carbonate concentrations the rare mineral lanarkite can form in conditions of pH between those for anglesite and leadhillite (JRS 18.11)

At Tsumeb, Namibia, leadhillite occurs with mimetite and melanotekite (R&M 90.2.185-186).

Leadhillite is found at several localities in Cumbria, England, UK:
At Balliway Rigg it has been found in cavities in oxidised galena in quartz veins, associated with caledonite, mattheddleite Pb5(SiO4)1.5(SO4)1.5Cl and lanarkite. It is sometimes associated with anglesite, cerussite or linarite (JRS 11.15-16).
At Red Gill Mine it occurs as crusts on quartz associated with numerous minerals including anglesite, linarite, caledonite, bindheimite, cerussite and susannite (JRS 11.38).
At Shortgrain leadhillite is common in the supergene post-mining assemblage, and in some specimens it replaces lanarkite. Crystals are also produced by in situ oxidation in the vein. It is often associated with its polymorphs susannite and macphersonite, and sometimes occurs with scotlandite, native silver or caledonite (JRS 12.54-55).
At Silver Gill leadhillite occurs associated with anglesite and caledonite (JRS 8(2).91-92).
At Driggith Mine dumps leadhillite occurs in oxidised galena-bearing fragments associated with caledonite, anglesite and cerussite (JRS 9.23).
At the Brae Fell Mine leadhillite occurs associated with anglesite, caledonite, cerussite and linarite (JRS 9.41).

At Whitwell quarry, Derbyshire, England, UK, leadhillite is associated with galena and baryte (RES p138).

At the Manila Mine in Arizona, USA, leadhillite occurs associated with anglesite, and in vugs with caledonite, diaboleite, linarite and lanarkite (R&M 90.4.344).

Heating leadhillite causes it to reversibly transform into its polymorph susannite in the temperature range from 50 to 82°C.

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