Pyromorphite
Encyclopedia
Pyromorphite is a mineral
species composed of lead
chlorophosphate: Pb
5(P
O
4)3Cl
, sometimes occurring in sufficient abundance to be mined as an ore
of lead. Crystal
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. It is part of a series with two other minerals: mimetite
(Pb5(As
O4)3Cl) and vanadinite
(Pb5(V
O4)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). The phosphate was first distinguished chemically by M. H. Klaproth
in 1784, and it was named pyromorphite by J. F. L. Hausmann
in 1813.
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
6.5 - 7.1. Owing to isomorphous replacement of the phosphorus
by arsenic
there may be a gradual passage from pyromorphite to mimetite. Varieties containing calcium
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 Mies
in Bohemia
, nussierite from Nuizière, Chénelette
, near Beaujeu
, Rhône
, France
, and cherokine from Cherokee County
in Georgia
.
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
species composed of lead
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
chlorophosphate: Pb
Lead
Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...
5(P
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
O
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
4)3Cl
Chlorine
Chlorine is the chemical element with atomic number 17 and symbol Cl. It is the second lightest halogen, found in the periodic table in group 17. The element forms diatomic molecules under standard conditions, called dichlorine...
, sometimes occurring in sufficient abundance to be mined as an ore
Ore
An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....
of lead. Crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
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. It is part of a series with two other minerals: mimetite
Mimetite
Mimetite, whose name derives from the Greek Μιμητής mimethes, meaning "imitator", is an arsenate mineral which forms as a secondary mineral in lead deposits, usually by the oxidation of galena and arsenopyrite. The name is a reference to mimetite's resemblance to the mineral pyromorphite...
(Pb5(As
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
O4)3Cl) and vanadinite
Vanadinite
Vanadinite is a mineral belonging to the apatite group of phosphates, with the chemical formula Pb53Cl. It is one of the main industrial ores of the metal vanadium and a minor source of lead. A dense, brittle mineral, it is usually found in the form of red hexagonal crystals. It is an uncommon...
(Pb5(V
Vanadium
Vanadium is a chemical element with the symbol V and atomic number 23. It is a hard, silvery gray, ductile and malleable transition metal. The formation of an oxide layer stabilizes the metal against oxidation. The element is found only in chemically combined form in nature...
O4)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). The phosphate was first distinguished chemically by M. H. Klaproth
Martin Heinrich Klaproth
Martin Heinrich Klaproth was a German chemist.Klaproth was born in Wernigerode. During a large portion of his life he followed the profession of an apothecary...
in 1784, and it was named pyromorphite by J. F. L. Hausmann
Johann Friedrich Ludwig Hausmann
Johann Friedrich Ludwig Hausmann was a German mineralogist.-Biography:He was born in Hanover and educated in Göttingen, where he obtained a Ph.D...
in 1813.
Lustre (mineralogy)
Lustre is a description of the way light interacts with the surface of a crystal, rock, or mineral. The word lustre traces its origins back to the Latin word lux, meaning "light", and generally implies radiance, gloss, or brilliance....
is resinous. The hardness is 3.5 to 4, and the specific gravity
Specific gravity
Specific gravity is the ratio of the density of a substance to the density of a reference substance. Apparent specific gravity is the ratio of the weight of a volume of the substance to the weight of an equal volume of the reference substance. The reference substance is nearly always water for...
6.5 - 7.1. Owing to isomorphous replacement of the phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
by arsenic
Arsenic
Arsenic is a chemical element with the symbol As, atomic number 33 and relative atomic mass 74.92. Arsenic occurs in many minerals, usually in conjunction with sulfur and metals, and also as a pure elemental crystal. It was first documented by Albertus Magnus in 1250.Arsenic is a metalloid...
there may be a gradual passage from pyromorphite to mimetite. Varieties containing calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
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 Mies
Mies
Mies is a municipality in the district of Nyon in the canton of Vaud in Switzerland.It is approximately half-way between Geneva and Nyon. Mies sits on Lake Geneva , which lies to the southeast and is 410m above sea-level. The highest point of Mies is 455m above sea level. The part of Mies touching...
in Bohemia
Bohemia
Bohemia is a historical region in central Europe, occupying the western two-thirds of the traditional Czech Lands. It is located in the contemporary Czech Republic with its capital in Prague...
, nussierite from Nuizière, Chénelette
Chénelette
Chénelette is a commune in the Rhône department in eastern France.-Geography:Chénelette is a small village of approximately 300 people located in the north-west of the Rhône Department, notably in the Beaujolais region. The surrounding landscape is one of forests, mountains , and pastures; and is...
, near Beaujeu
Beaujeu, Rhône
Beaujeu is a commune of the Rhône department in eastern France.It lies between Mâcon and Lyon.Beaujeu gives its name to the famous wine region of Beaujolais , a former province of France of which it is the historical capital...
, Rhône
Rhône (département)
Rhône is a French department located in the central Eastern region of Rhône-Alpes. It is named after the Rhône River.- History :The Rhône department was created on August 12, 1793 when the former département of Rhône-et-Loire was split into two departments: Rhône and Loire.Originally, the eastern...
, France
France
The French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France...
, and cherokine from Cherokee County
Cherokee County, Georgia
As of the census of 2000, there were 141,903 people, 49,495 households, and 39,200 families residing in the county. The population density was 335 people per square mile . There were 51,937 housing units at an average density of 123 per square mile...
in Georgia
Georgia (U.S. state)
Georgia is a state located in the southeastern United States. It was established in 1732, the last of the original Thirteen Colonies. The state is named after King George II of Great Britain. Georgia was the fourth state to ratify the United States Constitution, on January 2, 1788...
.