Formula: Pb5(PO4)3Cl
Phosphate, apatite group, apatite supergroup
Isostructural with mimetite and vanadinite
Crystal System: Hexagonal
Specific gravity: 7.04 measured, 7.109 calculated
Hardness: 3½ to 4
Streak: White
Colour: Green to dark green, yellow, greenish-yellow or yellowish-green, orangish-yellow, shades of brown; white and colourless when pure; colourless or faintly tinted in transmitted light
Solubility: Slightly soluble in hydrochloric acid and sulphuric acid; moderately soluble in nitric acid and KOH; slightly soluble in carbonated water (Mindat)
Common impurities: F,Ra,Ca,Cr,V,As

Hydrothermal environments

Pyromorphite is usually a secondary lead mineral found in the oxidation zones of high temperature hydrothermal lead deposits associated with other oxidised lead and zinc minerals. Lead will generally precipitate as primary galena from ore fluids rich in sulphur and lead. Removal of sulphur by precipitation of sulphides, however, may lead ultimately to an ore fluid from which galena cannot be precipitated, even with a high concentration of lead in solution. In these circumstances, pyromorphite, as well as cerussite and anglesite, could be precipitated as primary minerals (Strens (1963), MM 33:722-3).

Pyromorphite forms a complete series with mimetite (lead chloride arsenate), and many specimens are intermediates between the two end-members.
Pyromorphite forms pseudomorphs after galena and cerussite (common), and galena forms pseudomorphs after pyromorphite (Dana, JRS 12.38). Other pseudomorphs include apatite after pyromorphite and plumbogummite encrusted on and replacing pyromorphite (Mindat).

galena is sometimes epitaxial on pyromorphite.


At the Daoping Mine, Gongcheng County, Guilin, Guangxi, China, well formed deep green crystals of pyromorphite have been found (AESS).
Pyromorphite from Daoping - Image

At the Lingchuan Mine, Lingchuan County, Guilin, Guangxi, China, light yellowish green crystals of pyromorphite have been found (AESS).
Pyromorphite from Lingchuan - Image

At the Yangshuo Mine, Yangshuo County, Guilin, Guangxi, China, plumbogummite pseudomorphs after pyromorphite have been found (KL p204).
Pyromorphite from Yangshuo - Image

At Poullaouen, France, galena pseudomorphs after pyromorphite have been found (KL p210).
Pyromorphite from Poullaouen - Image

Pyromorphite forms in the oxidised areas of lead ores. The most beautiful Moroccan pyromorphite crystals are extracted from the old lead mine of Bou Iboulkhir, in the Western Meseta Moulay Bouazza region. The ore deposits form pyromorphite-rich veins hosted mainly by schists. Pyromorphite is found as translucent yellow to green, equant to elongate hexagonal prisms, generally millimeter in size, but rare crystals reach 2 cm in length. The mineralogy of the pyromorphite-bearing veins includes galena, iron-manganese oxides, cerussite and quartz (R&M 98.2.174-175).

At the Bou Iboulkhir Mine, Moulay Bouazza, Moulay Bouazza Caïdat, Aguelmous Cercle, Khénifra Province, Béni Mellal-Khénifra Region, Morocco, pyromorphite is typically yellow to yellow-green, but in a very few specimens a vivid green colour is observed. The colour correlates with the accessory or trace-element chemistry. Green crystals are richer in calcium, copper and arsenic, whereas the yellow ones are richer in chromium (R&M91-4:321).
Pyromorphite from Moulay Bouazza - Image

At the Berg Aukas mine, Grootfontein, Otjozondjupa Region, Namibia, light green microcrystals of pyromorphite have been found in dolomite-lined vugs associated with willemite and aragonite (R&M 96.2.132-133).

Pyromorphite in the Northern Pennines, England, UK, is of secondary origin, developed by alteration of galena in the presence of phosphate-bearing solutions percolating through the upper weathering zone of the deposits (JRS 1.3.81-82).

At Alderley Edge, Cheshire, England, UK, copper mineralised solutions percolated through porous sandstone and deposited barium, cobalt, copper, lead, vanadium and zinc minerals between the sand grains. Anhydrite formed as cement in permeable rocks, then baryte was deposited, followed by pyrite, chalcopyrite, sphalerite and galena. These minerals crystallised from highly saline, sulphate-rich brines, at a temperature of 50 to 60o C. About 65 million years ago the deposit was uplifted, and oxygenated ground water oxidised original sulphide minerals. Galena was oxidised to cerussite, anglesite and pyromorphite (RES pps 49-50). A wide range of compositions in the pyromorphite - mimetite series occurs, from virtually arsenate-free pyromorphite to phosphate-rich mimetite associated with wulfenite (JRS 5(2).99). A sample of galena with copper and pyromorphite has been found (RES p54).
Pyromorphite from Alderley Edge - Image

At Closehouse Mine, Lunedale, County Durham, England, UK pyromorphite forms thin encrustations on fracture surfaces of baryte, and in places on altered dolerite wallrock. A few specimens have been found which show pyromorphite encrusting galena (JRS 1.3.81-82).
Pyromorphite from Closehouse - Image

At Grasshill Mine, Teesdale, County Durham, England, UK, pyromorphite has been found in cavities, sometimes surrounding cores of galena which is in an advanced stage of alteration to cerussite (JRS 1.3.81-82).

At Whitfield Brow Mines, Weardale, County Durham, England, UK, pyromorphite occurs as crusts on shale and quartz, and also on galena some of which shows advanced alteration to cerussite (JRS 1.3.81-82).

At Force Crag Mine, Coledale, Above Derwent, Allerdale, Cumbria, England, UK, a small specimen has been found with an open face of matrix covered with a combination of matte black sphalerite, white cerussite and typical brownish pyromorphite (AESS).
Pyromorphite from Force Crag - Image

At Balliway Rigg, Caldbeck, Allerdale, Cumbria, England, UK, vivid greenish yellow botryoidal pyromorphite and olive coloured hexagonal crystals have been found on a quartz matrix (AESS).
Pyromorphite from Balliway Rigg - Image

At the Driggith South Mine, Caldbeck, Allerdale, Cumbria, England, UK, barrel-shaped crystals of moss-green pyromorphite to 1 mm occur on a quartz boxwork matrix with limonite (AESS).
Pyromorphite from Driggith - Image

At Dry Gill Mine, Caldbeck, Allerdale, Cumbria, England, UK, pyromorphite is found on a quartz matrix (AESS).
Pyromorphite from Dry Gill - Image

At Ingray Gill, Caldbeck, Allerdale, Cumbria, England, UK, pyromorphite crystals encrust mottramite on a number of specimens. These crystals, which are late in the supergene paragenesis, are ideal endmember pyromorphite (JRS 12.38).

At the Roughton Gill mines, Caldbeck, Cumbria, England, UK, pyromorphite is the most abundant supergene mineral. Pseudomorphs and epimorphs of pyromorphite after cerussite and hydrocerussite occur here, typically as microcrystalline crusts surrounding and replacing prismatic cerussite (JRS 11.21).
Pyromorphite from Roughton Gill - Image

At Iron Crag, Roughton Gill, Caldbeck, Allerdale, Cumbria, England, UK, pyromorphite occurs as light yellowish green vitreous and translucent crystals on a matrix of quartz or of goethite (AESS).
Pyromorphite from Iron Crag - Image

At Old Brandley Mine, Catbells, Keswick, Allerdale, Cumbria, England, UK, a specimen has been found of a quartz matrix with a vug containing iron oxide stained quartz crystals with a druzy over-growth of green pyromorphite (AESS).
Pyromorphite from the Old Brandley Mine - Image

At Wapping mine, Matlock Bath, Derbyshire, England, UK, pyromorphite occurs as alteration crusts on corroded galena, and also on fluorite and secondary baryte (which it seems to replace), associated with cerussite and a little anglesite (JRS 4(1).32).

At Whitwell quarry, Derbyshire, England, UK, pyromorphite pseudomorphs after cerussite have been found (KL p204).

At the Burgam mine, Shelve, Shropshire, England, UK, pyromorphite is associated with baryte and quartz (RES p283).
Pyromorphite from Burgam - Image

At Roar Hill, Ballater, Buchan Grampian, Scotland, UK, lead-bearing vein mineralisation was exposed during recent work carried out on an unmetalled vehicle track. A small temporary quarry exposed fluorite-bearing quartz veins and minor wulfenite in light-coloured granite. At a second site, a little further to the west, an oxidised galena-bearing quartz vein was exposed.
Pyromorphite occurs as lime-green to yellow crusts and thin coatings in quartz-lined cavities at the track location. Analyses suggest that minor OH is present in substitution for Cl in some specimens (JRS 22.33).

At Cystanog Mine, Carmarthen, Carmarthenshire, Wales, UK, pyromorphite has been found as weathered coatings on vein quartz (MW).
Pyromorphite from Cystanog - Image

At Nant Mine, Llangunnor, Carmarthenshire, Wales, UK, pyromorphite has been found encrusting massive baryte (MW).
Pyromorphite from the Aberdaunant Mine - Image

At Penycefn Mine, Bontgoch, and at Frongoch Mine, Devil's Bridge, both at Ceredigion, Wales, UK, pyromorphite has been found with cerussite (MW).

At Llechweddhelyg Mine, Penrhyncoch, Ceredigion, Wales, UK, pyromorphite has been found as crystals in vuggy goethite gossan (MW).
Pyromorphite from Llechweddhelyg - Image

At Bwlch Glas Mine, Tal-y-bont, Ceredigion, Wales, UK, pyromorphite has been found with wulfenite on surface dumps, and underground coating crystals of quartz (MW).
Pyromorphite from the Bwlch Glas Mine - Image

At Silver Rake, Halkyn Mountain, Flintshire, Wales, UK, pyromorphite has been found with cerussite coating galena (MW).

At the Kabwe mine, Central Province, Zambia, pyromorphite is commonly associated with tarbuttite (R&M 94.2.131-133).
Pyromorphite from Kabwe - Image


In an acid environment, provided by dissolved carbon dioxide making carbonic acid H2CO3, galena may be oxidised as follows:
PbS + 2O2 ↔ Pb2+ + (SO4)2-
Although phosphorus is more abundant (0.099%) in the Earth's crust than chlorine (0.017%), chlorine is widely distributed in the surface environment but phosphorus occurs only as a trace element in most environments. In addition, only small amounts of chlorine are required to form pyromorphite but phosphorous is a major constituent. Hence the availability of phosphorus is likely to be an important factor in the formation of pyromorphite, especially in an oxidised lead deposit where lead is abundant. The commonest source of phosphorus is phosphate rock, which is mostly apatite.
5Pb2+ (from galena) + 3(PO4)3- (from apatite) + Cl- (abundant) ⇌ Pb2+5(PO4)3-3Cl- (pyromorphite)
If phosphorous is not available, galena will weather to anglesite or cerussite depending on the acidity (CG).

Solubility of pyromorphite
Pb5(PO4)3Cl (solid) + 6H+ (aqueous) ⇌ 5Pb2+ (aqueous) + 3H2PO-4 (aqueous) + Cl- (aqueous)
(Min Mag June 1989 Vol 53 pp363-371)

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