Magnesiohastingsite
Encyclopedia
Magnesiohastingsite is a calcium
-containing amphibole
and a member of the hornblende
group. It is an inosilicate (chain silicate) with the formula NaCa2(Mg4Fe3+)Si6Al2O22(OH)2 and molar mass
864.69 g. In synthetic magnesiohastingsite it appears that iron occurs both as ferrous
iron Fe2+ and as ferric
iron Fe3+, but the ideal formula features only ferric iron. It was named in 1928 by Marland P. Billings
. The name is for its relationship to hastingsite and its magnesium
content. Hastingsite was named for the locality in Dungannon Township, Hastings County, Ontario, Canada.
Calcic (containing calcium) amphiboles include:
The hornbende group includes:
, point group
2/m, space group
C2/m. It has two formula units per unit cell (Z = 2). The unit cell parameters both for natural and for synthetic material are
a = 9.9 Å, b = 18.0 Å, c = 5.3 Å, β = 105°.
. The tetrahedra within a chain all point outwards in the same direction, and the chains are linked back-to-back by cations to form I-beams. The I-beams themselves are then linked together to form the complete structure.
. It is biaxial (-) with refractive indices for natural material in the range nα = 1.652 to 1.676, nβ = 1.661 to 1.695, nγ = 1.666 to 1.706. Synthetic material has nα = 1.642 to 1.657, nγ = 1.653 to 1.672. An increase in magnesium
content causes a decrease in refractive indices. The maximum birefringence
(the difference in refractive index between light travelling through the crystal with different polarizations) is δ = 0.012 to 0.033. The optic angle 2V is the angle between the two optic axes
in a biaxial
crystal. Measured values of 2V for this mineral vary widely from about 60° to 90°. It is also possible to calculate a theoretical value of 2V from the measured values of the refractive indices. The calculated value varies from 68° to 88°. The direction perpendicular to the plane containing the two optic axes is called the optical direction Y. In magnesiohastingsite Y is parallel to the b crystal axis. The optical direction Z lies in the plane containing the two optic axes and bisects the angle between them. In magnesiohastingsite the angle between Z and the c crystal axis is 15° to 19°. If the color of the incident light is changed, then the refractive indices are modified, and the value of 2V changes. This is known as dispersion of the optic axes
. For magnesiohastingsite the effect is weak, with 2V larger for red light than for violet light (r>v).
Pleochroism
is variable in green, yellow-green, bluish-green and brown.
is good with cleavage surfaces intersecting at about 56° and 124°, as is common with all the amphiboles. The mineral displays simple or multiple twinning
parallel to a prism face. It is a brittle mineral, with Mohs hardness 5 to 6 and specific gravity
3.2, with increasing magnesium content causing a decrease in specific gravity. It is not radioactive
and it is insoluble in hydrochloric acid
.
is in the Canadian National Railway
tunnel, Montreal
, Quebec, Canada. It is common in amphibolite
, schist
and pegmatitic
gabbro
. It is also found in welded tuffs, granodiorite
, granite
and tonalite
. Associated minerals include quartz
, orthoclase
, plagioclase
, biotite
, magnetite
and apatite
. Barkevikite and the magnesium-rich members of the hastingsite group are found in diorite
, essexite
and related calciium-rich rocks.
Localities include:
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...
-containing amphibole
Amphibole
Amphibole is the name of an important group of generally dark-colored rock-forming inosilicate minerals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures.-Mineralogy:...
and a member of the hornblende
Hornblende
Hornblende is a complex inosilicate series of minerals .It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....
group. It is an inosilicate (chain silicate) with the formula NaCa2(Mg4Fe3+)Si6Al2O22(OH)2 and molar mass
Molar mass
Molar mass, symbol M, is a physical property of a given substance , namely its mass per amount of substance. The base SI unit for mass is the kilogram and that for amount of substance is the mole. Thus, the derived unit for molar mass is kg/mol...
864.69 g. In synthetic magnesiohastingsite it appears that iron occurs both as ferrous
Ferrous
Ferrous , in chemistry, indicates a divalent iron compound , as opposed to ferric, which indicates a trivalent iron compound ....
iron Fe2+ and as ferric
Ferric
Ferric refers to iron-containing materials or compounds. In chemistry the term is reserved for iron with an oxidation number of +3, also denoted iron or Fe3+. On the other hand, ferrous refers to iron with oxidation number of +2, denoted iron or Fe2+...
iron Fe3+, but the ideal formula features only ferric iron. It was named in 1928 by Marland P. Billings
Marland P. Billings
Marland Pratt Billings was an American structural geologist who was considered one of the greatest authorities on North American geology. Billings was Professor of Geology at Harvard University for almost his entire career, having joined the faculty in 1930 and retired to emeritus status in 1972...
. The name is for its relationship to hastingsite and its 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...
content. Hastingsite was named for the locality in Dungannon Township, Hastings County, Ontario, Canada.
Calcic (containing calcium) amphiboles include:
- The tremoliteTremoliteTremolite is a member of the amphibole group of silicate minerals with composition: Ca2Mg5Si8O222. Tremolite forms by metamorphism of sediments rich in dolomite and quartz. Tremolite forms a series with actinolite and ferro-actinolite. Pure magnesium tremolite is creamy white, but the color grades...
-actinoliteActinoliteActinolite is an amphibole silicate mineral with the chemical formula .-Etymology:The name actinolite is derived from the Greek word aktis , meaning "beam" or "ray", because of the mineral's fibrous nature...
-ferro-actinolite series - The hornblendeHornblendeHornblende is a complex inosilicate series of minerals .It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole....
group - The kaersutiteKaersutiteKaersutite is a dark brown to black amphibole mineral with formula: NaCa2Si6Al2O232.It occurs as phenocrysts in alkalic volcanic rocks; in nodules of peridotite and gabbro in alkalic basalts; in syenites, monzonites and carbonatite tuffs...
-ferro-kaersutite series - Joesmithite
The hornbende group includes:
- The edeniteEdeniteEdenite is a double chain silicate mineral of the amphibole group with the general chemical composition Na[Ca2][Mg5[2|AlSi7O22]. Edenite is named for the locality of Edenville, Orange County, New York, where it was first described.- Occurrence :...
-ferro-edenite series - The tschermakiteTschermakiteThe endmember hornblende tschermakite is a calcium rich monoclinic amphibole mineral. It is frequently synthesized along with its ternary solid solution series members tremolite and cummingtonite so that the thermodynamic properties of its assemblage can be applied to solving other solid solution...
-ferrotschermakite series - The pargasitePargasitePargasite is a complex inosilicate mineral of the amphibole group with formula NaCa24AlO222.It was first described for an occurrence in Pargas, Finland in 1814 and named for the locality....
-ferro-pargasite series - The magnesiohastingsite-hastingsite series
- The magnesiosadanagaite-sadanagaite series
Unit cell
Magnesiohastingsite belongs to the monoclinic crystal systemMonoclinic 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...
, point group
Point group
In geometry, a point group is a group of geometric symmetries that keep at least one point fixed. Point groups can exist in a Euclidean space with any dimension, and every point group in dimension d is a subgroup of the orthogonal group O...
2/m, space group
Space 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...
C2/m. It has two formula units per unit cell (Z = 2). The unit cell parameters both for natural and for synthetic material are
a = 9.9 Å, b = 18.0 Å, c = 5.3 Å, β = 105°.
Structure
The structure of all amphiboles is based on a double chain of linked SiO4 tetrahedra, with composition (Si4O11)n. The inner tetrahedra are referred to as T1 and the outer ones as T2. The pattern in the double chain repeats after a block of two T1 and two T2 tetrahedra, with a repeat distance of approximately 5.3 Å, and this determines the length of the unit cell along the c crystal axisCrystal 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...
. The tetrahedra within a chain all point outwards in the same direction, and the chains are linked back-to-back by cations to form I-beams. The I-beams themselves are then linked together to form the complete structure.
Optical properties
The mineral is subopaque and vitreous, green to dark green or black in color and with a pale grey-green to pale brownish-green streakStreak (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...
. It is biaxial (-) with refractive indices for natural material in the range nα = 1.652 to 1.676, nβ = 1.661 to 1.695, nγ = 1.666 to 1.706. Synthetic material has nα = 1.642 to 1.657, nγ = 1.653 to 1.672. An increase in 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...
content causes a decrease in refractive indices. The maximum birefringence
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...
(the difference in refractive index between light travelling through the crystal with different polarizations) is δ = 0.012 to 0.033. The optic angle 2V is the angle between the two optic axes
Optic axis of a crystal
The optic axis of a crystal is the direction in which a ray of transmitted light suffers no birefringence . Due to the internal structure of the crystal , light propagates along the optical axis differently than in other directions...
in a biaxial
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...
crystal. Measured values of 2V for this mineral vary widely from about 60° to 90°. It is also possible to calculate a theoretical value of 2V from the measured values of the refractive indices. The calculated value varies from 68° to 88°. The direction perpendicular to the plane containing the two optic axes is called the optical direction Y. In magnesiohastingsite Y is parallel to the b crystal axis. The optical direction Z lies in the plane containing the two optic axes and bisects the angle between them. In magnesiohastingsite the angle between Z and the c crystal axis is 15° to 19°. If the color of the incident light is changed, then the refractive indices are modified, and the value of 2V changes. This is known as dispersion of the optic axes
Optic axis of a crystal
The optic axis of a crystal is the direction in which a ray of transmitted light suffers no birefringence . Due to the internal structure of the crystal , light propagates along the optical axis differently than in other directions...
. For magnesiohastingsite the effect is weak, with 2V larger for red light than for violet light (r>v).
Pleochroism
Pleochroism
Pleochroism is an optical phenomenon in which a substance appears to be different colors when observed at different angles with polarized light.- Background :Anisotropic crystals will have optical properties that vary with the direction of light...
is variable in green, yellow-green, bluish-green and brown.
Physical properties
CleavageCleavage (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...
is good with cleavage surfaces intersecting at about 56° and 124°, as is common with all the amphiboles. The mineral displays simple or multiple twinning
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....
parallel to a prism face. It is a brittle mineral, with Mohs hardness 5 to 6 and 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...
3.2, with increasing magnesium content causing a decrease in specific gravity. It is not radioactive
Radioactive decay
Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
and it is insoluble in hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....
.
Occurrence and associations
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....
is in the Canadian National Railway
Canadian National Railway
The Canadian National Railway Company is a Canadian Class I railway headquartered in Montreal, Quebec. CN's slogan is "North America's Railroad"....
tunnel, Montreal
Montreal
Montreal is a city in Canada. It is the largest city in the province of Quebec, the second-largest city in Canada and the seventh largest in North America...
, Quebec, Canada. It is common in amphibolite
Amphibolite
Amphibolite is the name given to a rock consisting mainly of hornblende amphibole, the use of the term being restricted, however, to metamorphic rocks. The modern terminology for a holocrystalline plutonic igneous rocks composed primarily of hornblende amphibole is a hornblendite, which are...
, schist
Schist
The schists constitute a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is...
and pegmatitic
Pegmatite
A pegmatite is a very crystalline, intrusive igneous rock composed of interlocking crystals usually larger than 2.5 cm in size; such rocks are referred to as pegmatitic....
gabbro
Gabbro
Gabbro refers to a large group of dark, coarse-grained, intrusive mafic igneous rocks chemically equivalent to basalt. The rocks are plutonic, formed when molten magma is trapped beneath the Earth's surface and cools into a crystalline mass....
. It is also found in welded tuffs, granodiorite
Granodiorite
Granodiorite is an intrusive igneous rock similar to granite, but containing more plagioclase than orthoclase-type feldspar. Officially, it is defined as a phaneritic igneous rock with greater than 20% quartz by volume where at least 65% of the feldspar is plagioclase. It usually contains abundant...
, granite
Granite
Granite is a common and widely occurring type of intrusive, felsic, igneous rock. Granite usually has a medium- to coarse-grained texture. Occasionally some individual crystals are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic...
and tonalite
Tonalite
Tonalite is an igneous, plutonic rock, of felsic composition, with phaneritic texture. Feldspar is present as plagioclase with 10% or less alkali feldspar. Quartz is present as more than 20% of the rock. Amphiboles and pyroxenes are common accessory minerals.In older references tonalite is...
. Associated minerals include 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,...
, orthoclase
Orthoclase
Orthoclase is an important tectosilicate mineral which forms igneous rock. The name is from the Greek for "straight fracture," because its two cleavage planes are at right angles to each other. Alternate names are alkali feldspar and potassium feldspar...
, plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
, biotite
Biotite
Biotite is a common phyllosilicate mineral within the mica group, with the approximate chemical formula . More generally, it refers to the dark mica series, primarily a solid-solution series between the iron-endmember annite, and the magnesium-endmember phlogopite; more aluminous endmembers...
, magnetite
Magnetite
Magnetite is a ferrimagnetic mineral with chemical formula Fe3O4, one of several iron oxides and a member of the spinel group. The chemical IUPAC name is iron oxide and the common chemical name is ferrous-ferric oxide. The formula for magnetite may also be written as FeO·Fe2O3, which is one part...
and apatite
Apatite
Apatite is a group of phosphate minerals, usually referring to hydroxylapatite, fluorapatite, chlorapatite and bromapatite, named for high concentrations of OH−, F−, Cl− or Br− ions, respectively, in the crystal...
. Barkevikite and the magnesium-rich members of the hastingsite group are found in diorite
Diorite
Diorite is a grey to dark grey intermediate intrusive igneous rock composed principally of plagioclase feldspar , biotite, hornblende, and/or pyroxene. It may contain small amounts of quartz, microcline and olivine. Zircon, apatite, sphene, magnetite, ilmenite and sulfides occur as accessory...
, essexite
Essexite
Essexite , also called nepheline monzogabbro , is a dark gray or black holocrystalline plutonic igneous rock. Its name is derived from the type locality in Essex County, MA.Modern petrology identifies rocks according to mineralogical criteria...
and related calciium-rich rocks.
Localities include:
- The granitic batholiths of the Scottish HighlandsScottish HighlandsThe Highlands is an historic region of Scotland. The area is sometimes referred to as the "Scottish Highlands". It was culturally distinguishable from the Lowlands from the later Middle Ages into the modern period, when Lowland Scots replaced Scottish Gaelic throughout most of the Lowlands...
- The Swiss and Italian AlpsAlpsThe Alps is one of the great mountain range systems of Europe, stretching from Austria and Slovenia in the east through Italy, Switzerland, Liechtenstein and Germany to France in the west....
- The HarzHarzThe Harz is the highest mountain range in northern Germany and its rugged terrain extends across parts of Lower Saxony, Saxony-Anhalt and Thuringia. The name Harz derives from the Middle High German word Hardt or Hart , latinized as Hercynia. The legendary Brocken is the highest summit in the Harz...
Mountains, Germany - Finland and Sweden
- Japan, where it is widespread
- The Southern CaliforniaCaliforniaCalifornia is a state located on the West Coast of the United States. It is by far the most populous U.S. state, and the third-largest by land area...
and Sierra Nevada batholiths, California, USA - LangbanLångbanLångban is a mining area in Värmland in Sweden. It belongs to Filipstad Municipality, with the nearest city being Filipstad, 21 km south. It was systematically mined through 1711-1972, but has traces from the 15th century. It is the birthplace of Swedish-American inventor John EricssonIt has...
, Sweden, in skarnSkarnSkarn is an old Swedish mining term originally used to describe a type of silicate gangue, or waste rock, associated with iron-ore bearing sulfide deposits apparently replacing Archean age limestones in Sweden's Persberg mining district. In modern usage the term "skarn" has been expanded to refer... - In a xenolithXenolithA xenolith is a rock fragment which becomes enveloped in a larger rock during the latter's development and hardening. In geology, the term xenolith is almost exclusively used to describe inclusions in igneous rock during magma emplacement and eruption...
in dioriteDioriteDiorite is a grey to dark grey intermediate intrusive igneous rock composed principally of plagioclase feldspar , biotite, hornblende, and/or pyroxene. It may contain small amounts of quartz, microcline and olivine. Zircon, apatite, sphene, magnetite, ilmenite and sulfides occur as accessory...
porphyryPorphyriticPorphyritic is an adjective used in geology, specifically for igneous rocks, for a rock that has a distinct difference in the size of the crystals, with at least one group of crystals obviously larger than another group...
in the Mount Hilliers complex, Henry MountainsHenry MountainsThe Henry Mountains are located in the southeastern portion of the U.S. state of Utah and run in a generally north-south direction, extending over a distance of about 30 miles . They were named by John Wesley Powell in honour of Joseph Henry, the first secretary of the Smithsonian Institution. The...
, Garfield County, Utah