Kutnohorite
Encyclopedia
Kutnohorite is a rare calcium
manganese
carbonate mineral with magnesium
and iron
, that is a member of the dolomite group. It forms a series with dolomite
, and with ankerite
. The end member formula is CaMn2+(CO3)2, but magnesium Mg and iron Fe2+ commonly substitute for manganese Mn2+, with the Mn content varying from 38% to 84%, so the formula Ca(Mn2+,Mg,Fe2+)(CO3)2 better represents the species. It was named by Professor Bukowsky in 1901 after the type locality
of Kutná Hora
, Bohemia, in the Czech Republic. It was originally spelt “kutnahorite” but “kutnohorite” is the current IMA-approved spelling.
R, the same as for the other members of the dolomite group. There are layers of (CO3)2- groups perpendicular to the long crystal axis
c, and between these layers there are layers of the cations Ca2+ and Mn2+. If there were perfect ordering amongst the cations they would separate into different layers, giving rise to the ordered sequence: Ca-(CO3)-Mn-(CO3)-Ca-(CO3)-Mn-(CO3)- along the c axis, not all specimens, however, display such ordering.
and the brown colours are due to increased iron
content. The mineral is translucent with a white to pale pink streak
and vitreous to dull luster
. It is uniaxial (-)
with refractive indices
No = 1.710 to 1.727 and Ne = 1.519 to 1.535, similar to dolomite. The ordinary refractive index
, No, is high, comparable with spinel
(1.719).
with curved faces, polycrystalline spherules and in massive and granular habits. It has perfect rhombohedral cleavage
, typical of carbonates. It is brittle with a subconchoidal fracture
and it is quite soft, with hardness 3½ to 4, between calcite
and fluorite
. Specific gravity
is 3.12, denser than both dolomite
and calcite. It is soluble in acids, as are all carbonates.
sediments, associated with rhodochrosite
, aragonite
and calcite
..
Notable occurrences include Tuscany
, Italy and Kutná Hora
, Czech Republic.
It probably occurs at the Trepča Mines
, Stari Trg, Kosovo, in the Balkans.
At the Eldorado Mine, Ouray County, Colorado
, USA, it occurs as tiny white crystals partially encrusting quartz
and dolomite
.
At the Ryujima Mine, Nagano Prefecture
in Japan, magnesian kutnohorite occurs with quartz
and rhodochrosite
.
The type locality
is Poličany, Kutná Hora
, Central Bohemia Region, Bohemia, Czech Republic, and type material is conserved at Harvard University
, Cambridge, Massachusetts, USA.
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...
manganese
Manganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
carbonate mineral with magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
and iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
, that is a member of the dolomite group. It forms a series with dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
, and with ankerite
Ankerite
Ankerite is a calcium, iron, magnesium, manganese carbonate mineral of the group of rhombohedral carbonates with formula: Ca2. In composition it is closely related to dolomite, but differs from this in having magnesium replaced by varying amounts of iron and manganese.The crystallographic and...
. The end member formula is CaMn2+(CO3)2, but magnesium Mg and iron Fe2+ commonly substitute for manganese Mn2+, with the Mn content varying from 38% to 84%, so the formula Ca(Mn2+,Mg,Fe2+)(CO3)2 better represents the species. It was named by Professor Bukowsky in 1901 after the type locality
Type locality (geology)
Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....
of Kutná Hora
Kutná Hora
Kutná Hora is a city in Bohemia, now the Czech Republic in the Central Bohemian Region.-History:The town began in 1142 with the settlement of the first Cistercian Monastery in Bohemia, Kloster Sedlitz, brought from the Imperial immediate Cistercian Waldsassen Abbey...
, Bohemia, in the Czech Republic. It was originally spelt “kutnahorite” but “kutnohorite” is the current IMA-approved spelling.
Dolomite group
- DolomiteDolomiteDolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
, CaMg(CO3)2 - AnkeriteAnkeriteAnkerite is a calcium, iron, magnesium, manganese carbonate mineral of the group of rhombohedral carbonates with formula: Ca2. In composition it is closely related to dolomite, but differs from this in having magnesium replaced by varying amounts of iron and manganese.The crystallographic and...
, CaFe2+(CO3)2 - Kutnohorite, CaMn2+(CO3)2
- Minrecordite, CaZn(CO3)2
Unit cell
There are three formula units per unit cell (Z = 3) and the lengths of the sides are a close to 4.9 Å and c between 16 Å and 17 Å, although different sources give slightly different values, as follows:- a = 4.915 Å, c = 16.639 Å
- a = 4.8518(3) Å, c = 16.217(2) Å
- a = 4.85 Å, c = 16.34 Å
Structure
The crystal class is trigonal , space groupSpace 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...
R, the same as for the other members of the dolomite group. There are layers of (CO3)2- groups perpendicular to the long crystal 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...
c, and between these layers there are layers of the cations Ca2+ and Mn2+. If there were perfect ordering amongst the cations they would separate into different layers, giving rise to the ordered sequence: Ca-(CO3)-Mn-(CO3)-Ca-(CO3)-Mn-(CO3)- along the c axis, not all specimens, however, display such ordering.
Optical properties
Kutnohorite may be white, pale pink or light brown. The pink shades are due to increased manganeseManganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
and the brown colours are due to increased iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
content. The mineral is translucent with a white to pale pink 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...
and vitreous to dull 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....
. It is uniaxial (-)
Birefringence
Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...
with refractive indices
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
No = 1.710 to 1.727 and Ne = 1.519 to 1.535, similar to dolomite. The ordinary refractive index
Birefringence
Birefringence, or double refraction, is the decomposition of a ray of light into two rays when it passes through certain anisotropic materials, such as crystals of calcite or boron nitride. The effect was first described by the Danish scientist Rasmus Bartholin in 1669, who saw it in calcite...
, No, is high, comparable with spinel
Spinel
Spinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4. Balas ruby is an old name for a rose-tinted variety.-Spinel group:...
(1.719).
Physical properties
Kutnohorite occurs as aggregates of bundled blades of white through rose pink to light brown crystals. Also as simple rhombsRhombus
In Euclidean geometry, a rhombus or rhomb is a convex quadrilateral whose four sides all have the same length. The rhombus is often called a diamond, after the diamonds suit in playing cards, or a lozenge, though the latter sometimes refers specifically to a rhombus with a 45° angle.Every...
with curved faces, polycrystalline spherules and in massive and granular habits. It has perfect rhombohedral 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...
, typical of carbonates. It is brittle with a subconchoidal fracture
Fracture (mineralogy)
In the field of mineralogy, fracture is a term used to describe the shape and texture of the surface formed when a mineral is fractured. Minerals often have a highly distinctive fracture, making it a principal feature used in their identification....
and it is quite soft, with hardness 3½ to 4, between calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
and 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...
. 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...
is 3.12, denser than both dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
and calcite. It is soluble in acids, as are all carbonates.
Occurrence
Kutnohorite occurs typically in manganiferousManganese
Manganese is a chemical element, designated by the symbol Mn. It has the atomic number 25. It is found as a free element in nature , and in many minerals...
sediments, associated with rhodochrosite
Rhodochrosite
Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO3. In its pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown. The streak is white. Its Mohs hardness varies between 3.5 and 4. Its specific gravity is 3.5 to 3.7. It...
, aragonite
Aragonite
Aragonite is a carbonate mineral, one of the two common, naturally occurring, crystal forms of calcium carbonate, CaCO3...
and calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
..
Notable occurrences include Tuscany
Tuscany
Tuscany is a region in Italy. It has an area of about 23,000 square kilometres and a population of about 3.75 million inhabitants. The regional capital is Florence ....
, Italy and Kutná Hora
Kutná Hora
Kutná Hora is a city in Bohemia, now the Czech Republic in the Central Bohemian Region.-History:The town began in 1142 with the settlement of the first Cistercian Monastery in Bohemia, Kloster Sedlitz, brought from the Imperial immediate Cistercian Waldsassen Abbey...
, Czech Republic.
It probably occurs at the Trepča Mines
Trepca Mines
The Trepča Mines was a huge industrial complex in Serbia, located in the Kosovska Mitrovica Municipality.With up to 23,000 employees, Trepča was once one of the biggest companies in socialist Yugoslavia. In the 1930s, a British company gained the rights to exploit the Stari Trg mine close to...
, Stari Trg, Kosovo, in the Balkans.
At the Eldorado Mine, Ouray County, Colorado
Ouray County, Colorado
Ouray County is one of the 64 counties of the State of Colorado in the United States. The county population was 3,742 at U.S. Census 2000. As of 2010, U.S. Census data place the population at 4,436. The county seat is the City of Ouray...
, USA, it occurs as tiny white crystals partially encrusting 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,...
and dolomite
Dolomite
Dolomite is a carbonate mineral composed of calcium magnesium carbonate CaMg2. The term is also used to describe the sedimentary carbonate rock dolostone....
.
At the Ryujima Mine, Nagano Prefecture
Nagano Prefecture
is a prefecture of Japan located in the Chūbu region of the island of Honshū. The capital is the city of Nagano.- History :Nagano was formerly known as the province of Shinano...
in Japan, magnesian kutnohorite occurs with 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,...
and rhodochrosite
Rhodochrosite
Rhodochrosite is a manganese carbonate mineral with chemical composition MnCO3. In its pure form, it is typically a rose-red color, but impure specimens can be shades of pink to pale brown. The streak is white. Its Mohs hardness varies between 3.5 and 4. Its specific gravity is 3.5 to 3.7. It...
.
The type locality
Type locality (geology)
Type locality , also called type area or type locale, is the where a particular rock type, stratigraphic unit, fossil or mineral species is first identified....
is Poličany, Kutná Hora
Kutná Hora
Kutná Hora is a city in Bohemia, now the Czech Republic in the Central Bohemian Region.-History:The town began in 1142 with the settlement of the first Cistercian Monastery in Bohemia, Kloster Sedlitz, brought from the Imperial immediate Cistercian Waldsassen Abbey...
, Central Bohemia Region, Bohemia, Czech Republic, and type material is conserved at Harvard University
Harvard University
Harvard University is a private Ivy League university located in Cambridge, Massachusetts, United States, established in 1636 by the Massachusetts legislature. Harvard is the oldest institution of higher learning in the United States and the first corporation chartered in the country...
, Cambridge, Massachusetts, USA.