Spurrite is a white, yellow or light blue

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. ...

with

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic ...

crystals. Its

chemical formula In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, ...

is Ca₅( Si O₄)₂ CO₃. Spurrite is generally formed in

contact 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 chem ...

zones as mafic magmas are intruded into

carbonate rock Carbonate rocks are a class of sedimentary rocks composed primarily of carbonate minerals. The two major types are limestone, which is composed of calcite or aragonite (different crystal forms of CaCO3), and dolomite rock (also known as doloston ...

s.Smith, J.V. (1960) "The Crystal structure of Spurrite, Ca₅(SiO₄)₂CO₃". ''Acta. Cryst.'' 13, 454 Spurrite's space group is P 2/a. It is biaxial with a birefringence of 0.0390–0.0400, giving second order red interference colors when viewed under crossed

polarizer A polarizer or polariser is an optical filter that lets light waves of a specific polarization pass through while blocking light waves of other polarizations. It can filter a beam of light of undefined or mixed polarization into a beam of well ...

s in a

petrographic microscope A petrographic microscope is a type of optical microscope used in petrology and optical mineralogy to identify rocks and minerals in thin sections. The microscope is used in optical mineralogy and petrography, a branch of petrology wh ...

. The

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar t ...

is in six-fold coordination with the

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as we ...

, the

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...

is in a four-fold coordination with the oxygen and the carbon is in two-fold coordination. One unique characteristic of spurrite is that it actually abides by two twin laws. Polysynthetic twinning can occur along its (001) and another type of twinning can occur parallel to its optical axes.

Discovery and occurrence

Spurrite was first described in 1908 for an occurrence in the Terneras Mine, Velardeña District,

Durango Durango (), officially named Estado Libre y Soberano de Durango ( en, Free and Sovereign State of Durango; Tepehuán: ''Korian''; Nahuatl: ''Tepēhuahcān''), is one of the 31 states which make up the 32 Federal Entities of Mexico, situated i ...

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 ...

. It was named for American economic geologist

Josiah Edward Spurr Josiah Edward Spurr (1870–1950) was an American geologist, explorer, and author. Born in Gloucester, Massachusetts, he was considered something of a failure as a youth, unsuited for the family fishing business, since on a voyage he invariably ...

(1870–1950). In addition to its type locality, spurrite has been reported from

Riverside County, California Riverside County is a county located in the southern portion of the U.S. state of California. As of the 2020 census, the population was 2,418,185, making it the fourth-most populous county in California and the 10th-most populous in the Uni ...

;

Luna County, New Mexico Luna County is a county located in the U.S. state of New Mexico. As of the 2010 census, the population was 25,095. Its county seat is Deming. This county abuts the Mexican border. Luna County comprises the Deming, NM Micropolitan Statistic ...

; and from the

Little Belt Mountains The Little Belt Mountains are a section of the Rocky Mountains in the U.S. state of Montana. Situated mainly in the Lewis and Clark National Forest, the mountains are used for logging and recreation for the residents of Great Falls, Montana. Show ...

Lewis and Clark County, Montana Lewis and Clark County is a county located in the U.S. state of Montana. As of the 2020 census, the population was 70,973. Its county seat is Helena, the state capital. The numerical designation for Lewis and Clark County (used in the issuance ...

. It is also found in Ireland, Scotland, New Zealand, Turkey, Israel, Japan and Siberia.

Cement manufacture contaminant

Spurrite forms as contaminating ''spurrite rings'' on the walls of cement kilns during the production of

Portland cement Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th cen ...

.Mosci, Ricardo, 1998, ''How To Eliminate Calcining Zone Rings'', Cement America http://cementamericas.com/mag/cement_eliminate_calcining_zone/

References

Nesosilicates Carbonate minerals Monoclinic minerals Minerals in space group 14 {{silicate-mineral-stub