Tsumcorite
Encyclopedia
Tsumcorite is a rare hydrated lead
arsenate
mineral that was discovered in 1971, and reported by Geier, Kautz and Muller. It was named after the TSUMeb CORporation mine at Tsumeb
, in Namibia, in recognition of the Corporation’s support for mineralogical investigations of the orebody at its Mineral Research Laboratory.
2/m, which means that it has a twofold axis of symmetry
along the b axis
and a mirror plane
perpendicular to this, in the plane containing the a and c axes. The a and c axes are inclined to each other at angle β = 115.3°. The unit cell parameters are a = 9.124 Å to 9.131 Å, b = 6.326 Å to 6.329 Å and c = 7.577 Å to 7.583 Å. There are two formula units per unit cell (Z = 2), and the space group
is C2/m, meaning that the cell is a C-face centred lattice, with lattice points in the center of the C face as well as at the corners of the cell. The structure is related to the brackebushite group structure.
Tsumcorite forms a series with helmutwinklerite as Zn replaces the Fe2+, with thometzekite as Cu replaces the Zn and Fe2+, and also with mawbyite.
, elongated along the b axis, or wedge-shaped. They occur in radiating sheaves and spherulites, and as fibrous crusts or earthy and powdery material. Cleavage
is good perpendicular to the c axis, and twinning is common.
Tsumcorite is yellow-brown, red-brown or orange in color, and it is one of the few minerals that have a yellow streak
(orpiment
and crocoite
are two others). It is translucent, with a vitreous luster
, and dichroic yellow to yellow-green. The optical class is biaxial and the refractive indices are approximately equal to 1.90.
The mineral is moderately hard, with a Mohs hardness of 4½, between fluorite
and apatite
, and quite heavy, due to the lead content, with specific gravity
5.2, which is more than baryte but less than cerussite
. It dissolves in hydrochloric acid
and it is not radioactive.
in the oxidized zone of some arsenic
-bearing hydrothermal lead
-zinc
deposits.
The type locality is the Tsumeb
Mine, Tsumeb, Otjikoto Region, Namibia, where it is associated with willemite
, smithsonite
, mimetite
, scorodite
, anglesite
, arseniosiderite
, beaverite, beudantite
, carminite, ludlockite, o’danielite, zincroselite, stranskiite and leiteite. At the Puttapa Mine
in Australia it occurs with adamite
, mimetite
, smithsonite
, goethite
and quartz
. At the Kintore Open Cut
, Broken Hill, Australia it occurs with segnitite, beudantite
, carminite and mawbyite.
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...
arsenate
Arsenate
The arsenate ion is AsO43−.An arsenate is any compound that contains this ion. Arsenates are salts or esters of arsenic acid.The arsenic atom in arsenate has a valency of 5 and is also known as pentavalent arsenic or As[V]....
mineral that was discovered in 1971, and reported by Geier, Kautz and Muller. It was named after the TSUMeb CORporation mine at Tsumeb
Tsumeb
Tsumeb is a city of 15,000 inhabitants and the largest town in Oshikoto region in northern Namibia. Tsumeb is the home of the world-famous Tsumeb mine, and the "gateway to the north" of Namibia. It is the closest town to the Etosha National Park...
, in Namibia, in recognition of the Corporation’s support for mineralogical investigations of the orebody at its Mineral Research Laboratory.
Unit cell
Tsumcorite belongs to the monoclinic crystal classMonoclinic crystal system
In crystallography, the monoclinic crystal system is one of the 7 lattice point groups. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal length, as in the orthorhombic system. They form a rectangular prism with a...
2/m, which means that it has a twofold axis of symmetry
Rotational symmetry
Generally speaking, an object with rotational symmetry is an object that looks the same after a certain amount of rotation. An object may have more than one rotational symmetry; for instance, if reflections or turning it over are not counted, the triskelion appearing on the Isle of Man's flag has...
along the b axis
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...
and a mirror plane
Reflection symmetry
Reflection symmetry, reflectional symmetry, line symmetry, mirror symmetry, mirror-image symmetry, or bilateral symmetry is symmetry with respect to reflection. That is, a figure which does not change upon undergoing a reflection has reflectional symmetry.In 2D there is a line of symmetry, in 3D a...
perpendicular to this, in the plane containing the a and c axes. The a and c axes are inclined to each other at angle β = 115.3°. The unit cell parameters are a = 9.124 Å to 9.131 Å, b = 6.326 Å to 6.329 Å and c = 7.577 Å to 7.583 Å. There are two formula units per unit cell (Z = 2), and the space group
Space group
In mathematics and geometry, a space group is a symmetry group, usually for three dimensions, that divides space into discrete repeatable domains.In three dimensions, there are 219 unique types, or counted as 230 if chiral copies are considered distinct...
is C2/m, meaning that the cell is a C-face centred lattice, with lattice points in the center of the C face as well as at the corners of the cell. The structure is related to the brackebushite group structure.
Mineral series
Tsumcorite belongs to the helmutwinklerite group, whose members are- tsumcorite PbZnFe2+(AsO4)2.H2O
- helmutwinklerite PbZn2(AsO4)2.2H2O
- thometzekite PbCu2+2(AsO4)2.2H2O
- mawbyite PbFe3+2(AsO4)2(OH)2
Tsumcorite forms a series with helmutwinklerite as Zn replaces the Fe2+, with thometzekite as Cu replaces the Zn and Fe2+, and also with mawbyite.
Crystal habit and Properties
Crystals are prismaticPrism (geometry)
In geometry, a prism is a polyhedron with an n-sided polygonal base, a translated copy , and n other faces joining corresponding sides of the two bases. All cross-sections parallel to the base faces are the same. Prisms are named for their base, so a prism with a pentagonal base is called a...
, elongated along the b axis, or wedge-shaped. They occur in radiating sheaves and spherulites, and as fibrous crusts or earthy and powdery material. Cleavage
Cleavage (crystal)
Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite crystallographic structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the...
is good perpendicular to the c axis, and twinning is common.
Tsumcorite is yellow-brown, red-brown or orange in color, and it is one of the few minerals that have a yellow streak
Streak (mineralogy)
The streak of a mineral is the color of the powder produced when it is dragged across an unweathered surface. Unlike the apparent color of a mineral, which for most minerals can vary considerably, the trail of finely ground powder generally has a more consistent characteristic color, and is thus...
(orpiment
Orpiment
Orpiment, As2S3, is a common monoclinic arsenic sulfide mineral. It has a Mohs hardness of 1.5 to 2 and a specific gravity of 3.46. It melts at 300 °C to 325 °C...
and crocoite
Crocoite
Crocoite is a mineral consisting of lead chromate, PbCrO4, and crystallizing in the monoclinic crystal system. It is sometimes used as a paint, being identical in composition with the artificial product chrome yellow. It was discovered at Berezovsky deposit near Ekaterinburg in the Urals in 1766;...
are two others). It is translucent, with a vitreous luster
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....
, and dichroic yellow to yellow-green. The optical class is biaxial and the refractive indices are approximately equal to 1.90.
The mineral is moderately hard, with a Mohs hardness of 4½, between fluorite
Fluorite
Fluorite is a halide mineral composed of calcium fluoride, CaF2. It is an isometric mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon...
and apatite
Apatite
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...
, and quite heavy, due to the lead content, with 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...
5.2, which is more than baryte but less than cerussite
Cerussite
Cerussite is a mineral consisting of lead carbonate , and an important ore of lead. The name is from the Latin cerussa, white lead. Cerussa nativa was mentioned by Conrad Gessner in 1565, and in 1832 F. S. Beudant applied the name cruse to the mineral, whilst the present form, cerussite, is due to...
. It dissolves in hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
and it is not radioactive.
Occurrence and Associations
Tsumcorite is a rare secondary mineralSupergene (geology)
In ore deposit geology, supergene processes or enrichment occur relatively near the surface. Supergene processes include the predominance of meteoric water circulation with concomitant oxidation and chemical weathering. The descending meteoric waters oxidize the primary sulfide ore minerals and...
in the oxidized zone of some 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...
-bearing hydrothermal 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...
-zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
deposits.
The type locality is the Tsumeb
Tsumeb
Tsumeb is a city of 15,000 inhabitants and the largest town in Oshikoto region in northern Namibia. Tsumeb is the home of the world-famous Tsumeb mine, and the "gateway to the north" of Namibia. It is the closest town to the Etosha National Park...
Mine, Tsumeb, Otjikoto Region, Namibia, where it is associated with willemite
Willemite
Willemite is a zinc silicate mineral and a minor ore of zinc. It is highly fluorescent under shortwave ultraviolet light.It occurs in all different colors in daylight, in fibrous masses, solid brown masses , and apple green gemmy masses.It was discovered in 1830 and named after William I of the...
, smithsonite
Smithsonite
Smithsonite, or zinc spar, is zinc carbonate , a mineral ore of zinc. Historically, smithsonite was identified with hemimorphite before it was realised that they were two distinct minerals. The two minerals are very similar in appearance and the term calamine has been used for both, leading to some...
, 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...
, scorodite
Scorodite
Scorodite is a common hydrated iron arsenate mineral, with the chemical formula FeAsO4·2H2O. It is found in hydrothermal deposits and as a secondary mineral in gossans worldwide. Scorodite weathers to limonite....
, anglesite
Anglesite
Anglesite is a lead sulfate mineral with the chemical formula PbSO4. It occurs as an oxidation product of primary lead sulfide ore, galena. Anglesite occurs as prismatic orthorhombic crystals and earthy masses, and is isomorphous with barite and celestine. It contains 74% of lead by mass and...
, arseniosiderite
Arseniosiderite
Arseniosiderite is a rare arsenate mineral formed by the oxidation of other arsenic-containing minerals, such as scorodite or arsenopyrite. It occurs in association with beudantite, carminite, dussertite, pharmacolite, pitticite, adamite and erythrite. The name arseniosiderite reflects two major...
, beaverite, beudantite
Beudantite
Beudandite is a secondary mineral occurring in the oxidized zones of polymetallic deposits. It is a lead, iron, arsenate, sulfate with endmember formula: PbFe36SO4AsO4....
, carminite, ludlockite, o’danielite, zincroselite, stranskiite and leiteite. At the Puttapa Mine
Beltana, South Australia
Beltana is a semi-ghost town north of Adelaide, South Australia. Beltana is known for continuing to exist long after the reasons for its existence had ceased...
in Australia it occurs with adamite
Adamite
Adamite is a zinc arsenate hydroxide mineral, Zn2AsO4OH. It is a mineral that typically occurs in the oxidized or weathered zone above zinc ore occurrences. Pure adamite is colorless, but usually it possess yellow color due to Fe compounds admixture. Tints of green also occur and are connected with...
, 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...
, smithsonite
Smithsonite
Smithsonite, or zinc spar, is zinc carbonate , a mineral ore of zinc. Historically, smithsonite was identified with hemimorphite before it was realised that they were two distinct minerals. The two minerals are very similar in appearance and the term calamine has been used for both, leading to some...
, goethite
Goethite
Goethite , named after the German polymath Johann Wolfgang von Goethe, is an iron bearing oxide mineral found in soil and other low-temperature environments. Goethite has been well known since prehistoric times for its use as a pigment. Evidence has been found of its use in paint pigment samples...
and quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
. At the Kintore Open Cut
Broken Hill Ore Deposit
The Broken Hill Ore Deposit is located underneath Broken Hill in western New South Wales, Australia, and is the namesake for the town. It is arguably the world's richest and largest zinc-lead ore deposit.- Discovery :...
, Broken Hill, Australia it occurs with segnitite, beudantite
Beudantite
Beudandite is a secondary mineral occurring in the oxidized zones of polymetallic deposits. It is a lead, iron, arsenate, sulfate with endmember formula: PbFe36SO4AsO4....
, carminite and mawbyite.