Bustamite
Encyclopedia
Bustamite is an calcium manganese inosilicate (chain silicate) and a member of the wollastonite
group. Magnesium, zinc and iron are common impurities substituting for manganese. It is a polymorph
of johannsenite, with bustamite as the high-temperature form of CaMnSi2O6 and johannsenite as the low temperature form. The inversion takes place at 830 °C, but may be very slow.
Bustamite could be confused with light-colored rhodonite
or pyroxmangite, but both these minerals are biaxial (+) whereas bustamite is biaxial (-).
Bustamite is a triclinic mineral, which could be described by a primitive unit cell, but the larger A-centered cell is often preferred, in order to facilitate comparison with the similar mineral wollastonite
.
The formula for bustamite is CaMn(SiO3)2 but it is sometimes written (Ca,Mn)SiO3, and changing the formula in this way will change the value of Z. The structure is chains of SiO4 tetraheda with repeat unit of three tetrahedra, unlike the pyroxenes where the repeat unit is two. Ca++ and Mn++ are positioned between the chains. There are 12 tetrahedra in the A-centered unit cell.
The unit cell, the formula and Z cannot be taken separately; they are interlinked and form a consistent set of values. In this article we adopt the A-centred unit cell (space group A) with a = 7.736 Å
, b = 7.157 Å and c = 13.824 Å, the formula CaMn(SO3)2 and Z = 6. Deer et al take the formula as (Mn,Ca,Fe)[SiO3] so their value of Z is doubled to 12. Mindat apparently gives the lattice parameters for a face-centred cell, although they give the space group as P.
was originally taken as Tetela de Jonotla, Puebla
, Mexico
, and the mineral was named for General Anastasio Bustamante (1780–1853), three times President of Mexico. The material from Puebla, however, was later found to be a mixture of johannsenite and rhodonite
, so the type locality is now the Franklin Mine
, Franklin, Sussex County, New Jersey
, USA.
Both bustamite and johansennite are found at Franklin. Bustamite is moderately common there and occurs in a variety of assemblages, associated with rhodonite
and tephroite
, calcite
and tephroite or glaucochroite
and tephroite. Vesuvianite
, wollastonite, garnet
, diopside
, willemite
, johannsenite, margarosanite and clinohedrite
also may be present.
of manganese-bearing sediments, with attendant metasomatism
. At the (new) type locality, Franklin, the oldest rocks are Precambrian
gneisses of mixed sedimentary and volcanic origin. Franklin Marble was deposited within these rocks, along with sediments containing zinc, manganese and iron minerals. These sediments were metamorphosed later in the Precambrian, then the rocks were uplifted from the late Precambrian into the Cambrian
and quartzite
was deposited on the eroded surface. In Cambrian-Ordovician
time the quartzite was in turn overlain by limestone
, and the rocks have been subject to uplift and erosion up to the present time.
Wollastonite
Wollastonite is a calcium inosilicate mineral that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or dolostone is subjected to high temperature and pressure sometimes in the presence of silica-bearing fluids...
group. Magnesium, zinc and iron are common impurities substituting for manganese. It is a polymorph
Polymorphism (materials science)
Polymorphism in materials science is the ability of a solid material to exist in more than one form or crystal structure. Polymorphism can potentially be found in any crystalline material including polymers, minerals, and metals, and is related to allotropy, which refers to chemical elements...
of johannsenite, with bustamite as the high-temperature form of CaMnSi2O6 and johannsenite as the low temperature form. The inversion takes place at 830 °C, but may be very slow.
Bustamite could be confused with light-colored rhodonite
Rhodonite
Rhodonite is a manganese inosilicate, SiO3 and member of the pyroxenoid group of minerals, crystallizing in the triclinic system...
or pyroxmangite, but both these minerals are biaxial (+) whereas bustamite is biaxial (-).
Cell parameters
There is considerable variety in the literature about the size and type of the unit cell, the formula to be used, and the value of Z, the number of formula units per unit cell.Bustamite is a triclinic mineral, which could be described by a primitive unit cell, but the larger A-centered cell is often preferred, in order to facilitate comparison with the similar mineral wollastonite
Wollastonite
Wollastonite is a calcium inosilicate mineral that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or dolostone is subjected to high temperature and pressure sometimes in the presence of silica-bearing fluids...
.
The formula for bustamite is CaMn(SiO3)2 but it is sometimes written (Ca,Mn)SiO3, and changing the formula in this way will change the value of Z. The structure is chains of SiO4 tetraheda with repeat unit of three tetrahedra, unlike the pyroxenes where the repeat unit is two. Ca++ and Mn++ are positioned between the chains. There are 12 tetrahedra in the A-centered unit cell.
The unit cell, the formula and Z cannot be taken separately; they are interlinked and form a consistent set of values. In this article we adopt the A-centred unit cell (space group A) with a = 7.736 Å
Ångström
The angstrom or ångström, is a unit of length equal to 1/10,000,000,000 of a meter . Its symbol is the Swedish letter Å....
, b = 7.157 Å and c = 13.824 Å, the formula CaMn(SO3)2 and Z = 6. Deer et al take the formula as (Mn,Ca,Fe)[SiO3] so their value of Z is doubled to 12. Mindat apparently gives the lattice parameters for a face-centred cell, although they give the space group as P.
Type locality
The type localityType 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....
was originally taken as Tetela de Jonotla, Puebla
Puebla
Puebla officially Estado Libre y Soberano de Puebla is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 217 municipalities and its capital city is Puebla....
, Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, and the mineral was named for General Anastasio Bustamante (1780–1853), three times President of Mexico. The material from Puebla, however, was later found to be a mixture of johannsenite and rhodonite
Rhodonite
Rhodonite is a manganese inosilicate, SiO3 and member of the pyroxenoid group of minerals, crystallizing in the triclinic system...
, so the type locality is now the Franklin Mine
Franklin Furnace
Franklin Furnace, also known as the Franklin Mine, is a famous mineral location for rare zinc, iron, manganese minerals in old mines in Franklin, New Jersey, USA. This locale produced more species of minerals and more different fluorescent minerals than any other location...
, Franklin, Sussex County, New Jersey
Sussex County, New Jersey
The County of Sussex is the northernmost county in the State of New Jersey. It is part of the New York City Metropolitan Area. As of the 2010 Federal decennial census, 149,265 persons resided in Sussex County...
, USA.
Both bustamite and johansennite are found at Franklin. Bustamite is moderately common there and occurs in a variety of assemblages, associated with rhodonite
Rhodonite
Rhodonite is a manganese inosilicate, SiO3 and member of the pyroxenoid group of minerals, crystallizing in the triclinic system...
and tephroite
Tephroite
Tephroite is a non-metallic manganese silicate mineral with the formula, Mn2SiO4.It was first described for an occurrence at the Sterling Hill Mine and Franklin, New Jersey, USA. It occurs in iron-manganese ore deposits and their related skarns. It also occurs in metamorphosed manganese-rich...
, 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 tephroite or glaucochroite
Glaucochroite
Glaucochroite is a calcium manganese nesosilicate mineral with formula: CaMnSiO4. It occurs in metamorphosed limestones.It was first described in 1899 in Franklin Furnace, Sussex County, New Jersey.- References :* * *...
and tephroite. Vesuvianite
Vesuvianite
Vesuvianite, also known as idocrase, is a green, brown, yellow, or blue silicate mineral. Vesuvianite occurs as tetragonal crystals in skarn deposits and limestones that have been subjected to contact metamorphism...
, wollastonite, garnet
Garnet
The garnet group includes a group of minerals that have been used since the Bronze Age as gemstones and abrasives. The name "garnet" may come from either the Middle English word gernet meaning 'dark red', or the Latin granatus , possibly a reference to the Punica granatum , a plant with red seeds...
, diopside
Diopside
Diopside is a monoclinic pyroxene mineral with composition MgCaSi2O6. It forms complete solid solution series with hedenbergite and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull green crystals in the monoclinic prismatic class...
, 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...
, johannsenite, margarosanite and clinohedrite
Clinohedrite
Clinohedrite is a rare silicate mineral. Its chemical composition is a hydrous calcium-zinc silicate; CaZn4·H2O. It crystallizes in the monoclinic system and typically occurs as veinlets and fracture coatings. It is commonly colorless, white to pale amethyst in color. It has perfect cleavage and...
also may be present.
Environment
Bustamite typically results from metamorphismMetamorphism
Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...
of manganese-bearing sediments, with attendant metasomatism
Metasomatism
Metasomatism is the chemical alteration of a rock by hydrothermal and other fluids.Metasomatism can occur via the action of hydrothermal fluids from an igneous or metamorphic source. In the igneous environment, metasomatism creates skarns, greisen, and may affect hornfels in the contact...
. At the (new) type locality, Franklin, the oldest rocks are Precambrian
Precambrian
The Precambrian is the name which describes the large span of time in Earth's history before the current Phanerozoic Eon, and is a Supereon divided into several eons of the geologic time scale...
gneisses of mixed sedimentary and volcanic origin. Franklin Marble was deposited within these rocks, along with sediments containing zinc, manganese and iron minerals. These sediments were metamorphosed later in the Precambrian, then the rocks were uplifted from the late Precambrian into the Cambrian
Cambrian
The Cambrian is the first geological period of the Paleozoic Era, lasting from Mya ; it is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latin name for Wales, where Britain's...
and quartzite
Quartzite
Quartzite is a hard metamorphic rock which was originally sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite is usually white to gray, though quartzites often occur in various shades of pink...
was deposited on the eroded surface. In Cambrian-Ordovician
Ordovician
The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...
time the quartzite was in turn overlain by limestone
Limestone
Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....
, and the rocks have been subject to uplift and erosion up to the present time.