Bustamite is a calcium manganese

inosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consi ...

(chain silicate) and a member of the

wollastonite Wollastonite is a calcium inosilicate mineral ( Ca Si O3) that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or dolomite is subjected to high temperature ...

group. Magnesium, zinc and iron are common impurities substituting for manganese. Bustamite is the high-temperature

polymorph Polymorphism, polymorphic, polymorph, polymorphous, or polymorphy may refer to: Computing * Polymorphism (computer science), the ability in programming to present the same programming interface for differing underlying forms * Ad hoc polymorphi ...

of CaMnSi₂O₆ and

johannsenite Johannsenite is a silicate mineral that is a member of the pyroxene family. The mineral can be produced in limestone or due a metamorphic process. The mineral is also associated with Pb-Zn Mineralization (geology), mineralization. It is a relativ ...

is the low temperature polymorph. The inversion takes place at , but may be very slow.Deer, W A, Howie, R A and Zussman, J (1978) Rock-Forming Minerals, 2nd edition, Volume 2A, pages 574-585
Bustamite could be confused with light-colored

rhodonite Rhodonite is a manganese inosilicate, (Mn, Fe, Mg, Ca)SiO3 and member of the pyroxenoid group of minerals, crystallizing in the triclinic system. It commonly occurs as cleavable to compact masses with a rose-red color (the name comes from the Gr ...

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 In geometry, biology, mineralogy and solid state physics, a unit cell is a repeating unit formed by the vectors spanning the points of a lattice. Despite its suggestive name, the unit cell (unlike a unit vector, for example) does not necessari ...

, the formula to be used, and the value of Z, the number of formula units per unit cell. Bustamite is a

triclinic 180px, Triclinic (a ≠ b ≠ c and α ≠ β ≠ γ ) In crystallography, the triclinic (or anorthic) crystal system is one of the 7 crystal systems. A crystal system is described by three basis vectors. In the triclinic system, the crystal i ...

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

.Peacor and Prewitt (1963) The American Mineralogist volume 48 pages 588 to 596 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 tetrahedra with repeat unit of three tetrahedra, unlike the

pyroxenes The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe II) ...

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) iO₃so 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 locality Type locality may refer to: * Type locality (biology) * Type locality (geology) See also * Local (disambiguation) * Locality (disambiguation) {{disambiguation ...

was originally taken as Tetela de Jonotla,

Puebla Puebla ( en, colony, settlement), officially Free and Sovereign State of Puebla ( es, Estado Libre y Soberano de Puebla), is one of the 32 states which comprise the Federal Entities of Mexico. It is divided into 217 municipalities and its cap ...

Mexico Mexico ( Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guate ...

, and the mineral was named for the Mexican mineralogist and botanist Miguel Bustamante y Septiem (1790–1844). The material from Puebla, however, was later found to be a mixture of

and

,Dana's New Mineralogy Eighth Edition, Wiley so the type locality is now the Franklin Mine, Franklin,

Sussex County, New Jersey Sussex County is the northernmost county in the State of New Jersey. Its county seat is Newton. ...

, US. Both bustamite and johansennite are found at Franklin.http://franklin-sterlinghill.com/dunn/ch17/bustamite.stm Bustamite is moderately common there and occurs in a variety of assemblages, associated with

and

tephroite Tephroite is the manganese endmember of the olivine group of nesosilicate minerals with the formula Mn2 Si O4. A solid solution series exists between tephroite and its analogues, the group endmembers fayalite and forsterite. Divalent iron or ...

calcite Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scra ...

and tephroite or glaucochroite and tephroite.

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. It was first discovered with ...

, wollastonite,

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. All species of garnets possess similar physical properties and crystal forms, but differ in chemical composition. The different ...

diopside Diopside is a monoclinic pyroxene mineral with composition . It forms complete solid solution series with hedenbergite () and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dul ...

willemite Willemite is a zinc silicate mineral () and a minor ore of zinc. It is highly fluorescent (green) under shortwave ultraviolet light. It occurs in a variety of colors in daylight, in fibrous masses and apple-green gemmy masses. Troostite is a vari ...

, johannsenite, margarosanite and clinohedrite also may be present.

Environment

Bustamite typically results from

metamorphism Metamorphism is the transformation of existing rock (the protolith) to rock with a different mineral composition or texture. Metamorphism takes place at temperatures in excess of , and often also at elevated pressure or in the presence of ...

of manganese-bearing sediments, with attendant

metasomatism Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is the replacement of one rock by another of different mineralogical and chemical c ...

. At the (new) type locality, Franklin, the oldest rocks are

Precambrian The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of th ...

gneisses Gneiss ( ) is a common and widely distributed type of metamorphic rock. It is formed by high-temperature and high-pressure metamorphic processes acting on formations composed of igneous or sedimentary rocks. Gneiss forms at higher temperatures an ...

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 The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ag ...

and

quartzite Quartzite is a hard, non- foliated metamorphic rock which was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tec ...

was deposited on the eroded surface. In Cambrian-

Ordovician The Ordovician ( ) is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start of the Silurian Period Mya. ...

time the quartzite was in turn overlain by

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

, and the rocks have been subject to uplift and erosion up to the present time.Drake, A A (1990) The regional geologic setting of the Franklin-Sterling Hill district. Symposium on the character and origin of the Franklin-Sterling Hill orebodies, Proceedings, pp. 14-31, Lehigh University, Bethlehem, Pennsylvania

References

External links

{{Commons category, Bustamite Inosilicates Triclinic minerals Minerals in space group 2