Spurrite
Encyclopedia
Spurrite is a white, yellow or light blue mineral
with monoclinic
crystals. Its chemical formula
is Ca
5(Si
O
4)2C
O3.
Spurrite is generally formed in contact metamorphism zones as mafic magma
s are intruded into carbonate rock
s. 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
s in a petrographic microscope
.
The calcium
is in six-fold coordination with the oxygen
, the silicon
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.
, Mexico
. It was named for American economic geologist, Josiah Edward Spurr (1870-1950).
In addition to its type locality, spurrite has been reported from Riverside County, California
; Luna County, New Mexico
; and from the Little Belt Mountains
, Lewis and Clark County, Montana
. It is also found in Ireland, Scotland, New Zealand, Turkey, Israel, Japan and Siberia.
.
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
with monoclinic
Monoclinic 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...
crystals. Its chemical formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
is Ca
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...
5(Si
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
O
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
4)2C
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
O3.
Spurrite is generally formed in contact metamorphism zones as mafic magma
Mafic
Mafic is an adjective describing a silicate mineral or rock that is rich in magnesium and iron; the term is a portmanteau of the words "magnesium" and "ferric". Most mafic minerals are dark in color and the relative density is greater than 3. Common rock-forming mafic minerals include olivine,...
s are intruded into carbonate rock
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 and dolostone, which is composed of the mineral dolomite .Calcite can be either dissolved by groundwater or precipitated by...
s. 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
Polarizer
A polarizer is an optical filter that passes light of a specific polarization and blocks waves of other polarizations. It can convert a beam of light of undefined or mixed polarization into a beam with well-defined polarization. The common types of polarizers are linear polarizers and circular...
s in a petrographic microscope
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 which focuses on detailed descriptions of rocks...
.
The calcium
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...
is in six-fold coordination with the oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
, the silicon
Silicon
Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...
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
Crystal twinning
Crystal twinning occurs when two separate crystals share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals in a variety of specific configurations. A twin boundary or composition surface separates the two crystals....
. 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, DurangoDurango
Durango officially Estado Libre y Soberano de Durango is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. The state is located in Northwest Mexico. With a population of 1,632,934, it has Mexico's second-lowest population density, after Baja...
, 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...
. It was named for American economic geologist, Josiah Edward Spurr (1870-1950).
In addition to its type locality, spurrite has been reported from Riverside County, California
Riverside County, California
Riverside County is a county in the U.S. state of California. One of 58 California counties, it covers in the southern part of the state, and stretches from Orange County to the Colorado River, which forms the state border with Arizona. The county derives its name from the city of Riverside,...
; Luna County, New Mexico
Luna County, New Mexico
-2010:Whereas according to the 2010 U.S. Census Bureau:*77.7% White*1.1% Black*1.3% Native American*0.5% Asian*0.0% Native Hawaiian or Pacific Islander*2.6% Two or more races*16.8% Other races*61.5% Hispanic or Latino -2000:...
; and from the Little Belt Mountains
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...
, Lewis and Clark County, Montana
Lewis and Clark County, Montana
-National protected areas:* Flathead National Forest * Helena National Forest * Lewis and Clark National Forest * Lolo National Forest * Rocky Mountain Front Conservation Area -Demographics:...
. 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 cementPortland cement
Portland cement is the most common type of cement in general use around the world because it is a basic ingredient of concrete, mortar, stucco and most non-specialty grout...
.