Pyromorphite is a

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

species composed of

lead Lead () is a chemical element; it has Chemical symbol, symbol Pb (from Latin ) and atomic number 82. It is a Heavy metal (elements), heavy metal that is density, denser than most common materials. Lead is Mohs scale, soft and Ductility, malleabl ...

chlorophosphate: Pb₅( P O₄)₃ Cl, sometimes occurring in sufficient abundance to be mined as an

ore Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. The grade of ore refers to the concentration ...

of lead.

Crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

s are common, and have the form of a hexagonal prism terminated by the basal planes, sometimes combined with narrow faces of a hexagonal pyramid. Crystals with a barrel-like curvature are not uncommon. Globular and reniform masses are also found. Pyromorphite is part of the

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

group of minerals and bears a close resemblance physically and chemically with two other minerals:

mimetite Mimetite is a lead arsenate chloride mineral () which forms as a secondary mineral in lead deposits, usually by the Redox, oxidation of galena and arsenopyrite. The name derives from the Greek ''mimetes'', meaning "imitator" and refers to mimeti ...

(Pb₅( AsO₄)₃Cl) and

vanadinite Vanadinite is a mineral belonging to the apatite group of Phosphate minerals, phosphates, with the chemical formula lead, Pb5(vanadium, Voxygen, O4)3chlorine, Cl. It is one of the main industrial ores of the metal vanadium and a minor source of ...

(Pb₅( VO₄)₃Cl). The resemblance in external characters is so close that, as a rule, it is only possible to distinguish between them by chemical tests. They were formerly confused under the names green lead ore and brown lead ore (''German: Grünbleierz and Braunbleierz'').

History

The mineral was first distinguished chemically by M. H. Klaproth in 1784, and it was named pyromorphite by J. F. L. Hausmann in 1813. The name is derived from the Greek for ''pyr'' (fire) and ''morfe'' (form) due to its crystallization behavior after being melted.

Properties

The color of the mineral is usually some bright shade of green, yellow or brown, and the luster is resinous. The hardness is 3.5 to 4, and the

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

between 6.5 and 7.1.

Isomorphism

Owing to isomorphous replacement of the

phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...

arsenic Arsenic is a chemical element; it has Symbol (chemistry), symbol As and atomic number 33. It is a metalloid and one of the pnictogens, and therefore shares many properties with its group 15 neighbors phosphorus and antimony. Arsenic is not ...

there may be a gradual passage from pyromorphite to mimetite. Varieties containing

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

isomorphously replacing lead are lower in density (specific gravity 5.9–6.5) and usually lighter in color; they bear the names polysphaerite (because of the globular form), miesite from

Stříbro Stříbro (; ) is a town in Tachov District in the Plzeň Region of the Czech Republic. It has about 8,100 inhabitants. The historic town centre with the Renaissance Stříbro bridge is well preserved and is protected as an Cultural monument (Czech ...

(pronounced ''Mies'' in German) in

Bohemia Bohemia ( ; ; ) is the westernmost and largest historical region of the Czech Republic. In a narrow, geographic sense, it roughly encompasses the territories of present-day Czechia that fall within the Elbe River's drainage basin, but historic ...

, nussierite from Nuizière, Chénelette, near Beaujeu,

Rhône The Rhône ( , ; Occitan language, Occitan: ''Ròse''; Franco-Provençal, Arpitan: ''Rôno'') is a major river in France and Switzerland, rising in the Alps and flowing west and south through Lake Geneva and Southeastern France before dischargi ...

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

, and cherokine from Cherokee County in

Georgia Georgia most commonly refers to: * Georgia (country), a country in the South Caucasus * Georgia (U.S. state), a state in the southeastern United States Georgia may also refer to: People and fictional characters * Georgia (name), a list of pe ...

Biology

'' Paecilomyces javanicus'' is a

fungus A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

collected from a lead-polluted soil that is able to form biominerals of pyromorphite.

Gallery

File:Pyromorphite-137773.jpg, A pocket of crystals of pyromorphite from China File:Pyromorphite-157594.jpg, Miniature of sharp, lustrous, apple green color crystal "sprays" on matrix File:Pyromorphite-137954.jpg, Fine crystals of pyromorphite from Daoping Mine, Guangxi Zhuang Autonomous Region, China File:Pyromorphite-118273.jpg, Green pyromorphite crystals densely carpet the display side of the large matrix File:Pyromorphite-Cerussite-Caledonite-278353.jpg, Green pyromorphite microcrystals cover the vuggy, quartz-rich matrix. Seams of tiny

cerussite Cerussite (also known as lead carbonate or white lead ore) is a mineral consisting of lead carbonate with the chemical formula PbCO3, and is an important ore of lead. The name is from the Latin ''cerussa'', white lead. ''Cerussa nativa'' was ...

crystals and crusts of contrasting, powder-blue caledonite round out this very rich lead ore specimen from an old Leadhills mine.

References

External links

*{{EB1911, wstitle=Pyromorphite, volume=22, pages=693–694 Lead minerals Phosphate minerals Halide minerals Hexagonal minerals Minerals in space group 176 Luminescent minerals