Wadsleyite
Encyclopedia
Wadsleyite is a high-pressure polymorph
of olivine
, an orthorhombic mineral
found in the Peace River meteorite
in Alberta, Canada. In the phase transformations from Mg2SiO4-Fe2SiO4 (forsterite
-fayalite
), olivine is transformed to wadsleyite β-Mg2SiO4 and then to a spinel
-structured γ-Mg2SiO4 with increasing pressure. This series of transformations is thought to occur during an extraterrestrial shock event on the earth. With a formula of (Mg,Fe2+)2(SiO4), its cell parameters are as follows: a = 5.7Å, b = 11.7Å and c = 8.24Å. It is polymorphous with ringwoodite
and is found to be stable in the transition zone of the Earth’s upper mantle. These regions are between 400 and 525km in depth. Because of oxygens not bound to silicon in the Si2O7 groups of wadsleyite, it leaves oxygens unoccupied, and as a result, these oxygens are hydrated easily. As a result, there are high concentrations of hydrogen atoms in the mineral. Hydrous wadsleyite is a considered a potential site for water storage in the Earth’s mantle due to its low electrostatic potential. It exists with a hydrous melt at transition zone pressure-temperature conditions. The water solubility and density of wadsleyite is ultimately affected by the temperature and pressure inside of the Earth.
Wadsleyite was first pointed out by Ringwood and Major in 1966 and was confirmed to be a stable phase by Akimoto and Sato in 1968. (Horiuchi and Sawamoto, 1981) The phase was originally known as β-Mg2SiO4 or “Phase B” and is a polymorph of olivine, along with minerals ringwoodite
. Finally, wadsleyite was named after Dr. Arthur David Wadsley in his honor of his contributions to the field of geology.
Mg2SiO4, an end-member of the solid-solution series of olivine. (Horiuchi and Sawamoto, 1981) In the phase transformations of forsterite to fayalite
Mg2SiO4-Fe2SiO4, this magnesium-rich olivine α-Mg2SiO4 changes to wadsleyite β-Mg2SiO4 under certain pressure and temperature conditions, and then with increasing pressure, it transforms to γ-Mg2SiO4 which is a spinel
structure. (Agrell, Price, Putnis and Smith, 1983) Wadsleyite is synthesized stably at 1400˚C and under 17GPa of pressure between depths of 410 and 660km. Figure 1 shows the high pressure phases of olivine
polymorphs beginning with wadsleyite β-Mg2SiO4. Geologically speaking, it is a very fine-grained “reactive” forsterite that had been synthesized from hydrous starting materials.
In values of weight percent oxide, the pure magnesian variety of wadsleyite would be 44.5% SiO2, 52.2% MgO, and 3.33% H2O. The average microprobe analysis for wadsleyite yielded: MgO 38.21, SiO2 38.7, CaO 0.07, Cr2O3 0.01, MnO 0.43, GeO 22.37, NiO 0.11 and ZnO 0.10. (Smyth, 1987) A recalculation of the number of cations on the basis of four oxygens will yield MgO 1.51, SiO2 1.03, CaO 0.0019, Cr2O3 0.0002, MnO 0.0096, GeO 0.4032, NiO 0.0023 and ZnO 0.0019.
An analysis of trace elements in wadsleyite suggests that there are a number of elements included in it. Results demonstrate traces of rubidium
Rb, strontium
Sr, barium
Ba, titanium
Ti, zirconium
Zr, niobium
Nb, hafnium
Hf, tantalum
Ta, thorium
Th, and uranium
U in wadsleyite relative to olivine. (Fujii, Mibe, Nakai and Orihashi, 2006) This information suggests that the concentrations of these elements could be larger than what has been supposed in the transition zone of Earth’s upper mantle. Moreover, these results help in understanding chemical differentiation and magmatism inside the Earth. (Fujii, Mibe, Nakai and Orihashi, 2006)
meteorite
in Peace River, Alberta, Canada. This meteorite, an L6 hypersthene
-olivine chrondite, is believed to have formed during an extraterrestrial shock event on earth, beginning a solution-series of olivine. It occurs as microcrystalline rock fragments, often not surpassing 0.5mm in diameter, that pseudomorph
pre-existing olivine parts within the mineral. (Agrell, Price, Putnis and Smith, 1983) To the left, Figure 2 shows a microcrystalline image of wadsleyite. The meteor or asteroid
that impacted the earth generated the mineral phase transformations observed in shocked chrondites of the Peace River meteorite. (Beck, Gillet, Jahn, McMillan, Reynard, Van De Moortele and Wilson, 2007) It contains sulfide-rich veins of olivine and is believed, like other meteorite specimens, to have undergone a shock event, causing the grain components of olivine to transform into significant amounts of high-density wadsleyite. (Agrell, Price, Putnis and Smith, 1983)
and the silicon
are completely ordered in the structure. The hydrated O2 atom lies at the center of four edge-sharing Mg3+ octahedra. The compression of the unoccupied oxygen polyhedra plays a significant role in density increase of “pressure-induced” segments of transformations. (Smyth, 1994) This mineral contains three distinct tetrahedral sites, six different octahedral sites and eight distinct oxygen sites. (Kleppe, 2006) .The Mg3+ atoms occupy the octahedral sites; Si4+ atoms occupy the tetrahedral sites. Within the oxygen sites, some oxygens are unoccupied in the polyhedra, creating a shallow electrostatic potential for the mineral. (Horiuchi and Sawamoto, 1981)This meets the criteria for potential hydroxyl sites, in which the unoccupied oxygens become hydrated.
Wadsleyite is a pyrosilicate and a polymerized tetrahedral in which mostly Si2O7 groups are present. (Ashbrook, Berry, Farnanf, Le Polle, Pickard and Wimperise, 2006) A structure of β-Mg2SiO4 is shown in Figure 3. Wadsleyite II has both a single (SiO4) and coupled tetrahedral (Si2O7). It is a hydrous magnesium-iron silicate
with variable composition that occurs between the stability regions of wadsleyite and ringwoodite
γ-Mg2SiO4. (Kleppe, 2006) One-fifth of the silicon atom is in isolated tetrahedral and four-fifths is in Si2O7 groups so that the structure can be thought of as a mixture of one-fifth spinel and four-fifths wadsleyite. (Horiuchi and Sawamoto, 1981)
In the phase of wadsleyite II, there is considered to be possible host hydrogen
in the transition zone of the Earth’s mantle. Since forsterite is thought to be about or little over 50% of the mantle, the transition region in the upper mantle
could be an important water reservoir. (Kleppe, 2006) Wadsleyite is very water soluble and can accept up to 3 wt. % H2O as hydroxyl
at this site. Its water content is very significant in understanding the way Earth developed. Synthetic hydrous wadsleyite II is pictured in Figure 4. Wadsleyite II in a variably hydrous magnesium-iron silicate
phase. It is a potential host for hydrogen in the transition zone of the Earth's mantle. However, if the water composition of wadsleyite surpasses a 0.1–0.2 wt% amount, it could cause partial melting. As a result, an upwelling flow of water could affect the distribution of particular elements in the Earth. (Huang, Karato and Xu, 2005)
The wadsleyite minerals generally have a felsitic texture and are fractured. Because of small crystal size, detailed optical data could not be obtained; however, wadsleyite is anisotropic with low first-order birefringence
colors. (Agrell, Price, Putnis and Smith, 1983) Its mean refractive index
is n = 1.76, D = 3.84 and it is biaxial. In X-ray powder diffraction
, its strongest points in pattern are: 2.886(50)(040), 2.691(40)(013), 2.452(100,141), 2.038(80)(240), 1.442(80)(244). (Agrell, Price, Putnis and Smith, 1983)
of minerals and other inorganic compounds. (Agrell, Price, Putnis and Smith, 1983) His impressive investigations of minerals were all known to the mass in his field and to many others in the studies of geology. The proposal to have Wadsleyite named after Wadsley was approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association
. (Agrell, Price, Putnis and Smith, 1983) It is now preserved as an official mineral specimen in the Department of Geology’s collection at the University of Alberta. Dr. Wadsley accepted this honor for his exceptional knowledge in the geologic field of study.
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 olivine
Olivine
The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....
, an orthorhombic mineral
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...
found in the Peace River meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
in Alberta, Canada. In the phase transformations from Mg2SiO4-Fe2SiO4 (forsterite
Forsterite
Forsterite is the magnesium rich end-member of the olivine solid solution series. Forsterite crystallizes in the orthorhombic system with cell parameters a 4.75 Å , b 10.20 Å and c 5.98 Å .Forsterite is associated with igneous and metamorphic rocks and has also been found in meteorites...
-fayalite
Fayalite
Fayalite is the iron-rich end-member of the olivine solid-solution series. In common with all minerals in the olivine group, fayalite crystallizes in the orthorhombic system with cell parameters a 4.82 Å, b 10.48 Å and c Å 6.09.Iron rich olivine is a relatively common constituent of acidic and...
), olivine is transformed to wadsleyite β-Mg2SiO4 and then to a spinel
Spinel
Spinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4. Balas ruby is an old name for a rose-tinted variety.-Spinel group:...
-structured γ-Mg2SiO4 with increasing pressure. This series of transformations is thought to occur during an extraterrestrial shock event on the earth. With a formula of (Mg,Fe2+)2(SiO4), its cell parameters are as follows: a = 5.7Å, b = 11.7Å and c = 8.24Å. It is polymorphous with ringwoodite
Ringwoodite
Ringwoodite is a high-pressure polymorph of olivine, and it is stable at high temperatures and pressures like those in the Earth's mantle near 600 km depth. This mineral was first identified in the Tenham Meteorites in 1969, and it is inferred to be present in large quantity in the earth’s...
and is found to be stable in the transition zone of the Earth’s upper mantle. These regions are between 400 and 525km in depth. Because of oxygens not bound to silicon in the Si2O7 groups of wadsleyite, it leaves oxygens unoccupied, and as a result, these oxygens are hydrated easily. As a result, there are high concentrations of hydrogen atoms in the mineral. Hydrous wadsleyite is a considered a potential site for water storage in the Earth’s mantle due to its low electrostatic potential. It exists with a hydrous melt at transition zone pressure-temperature conditions. The water solubility and density of wadsleyite is ultimately affected by the temperature and pressure inside of the Earth.
Wadsleyite was first pointed out by Ringwood and Major in 1966 and was confirmed to be a stable phase by Akimoto and Sato in 1968. (Horiuchi and Sawamoto, 1981) The phase was originally known as β-Mg2SiO4 or “Phase B” and is a polymorph of olivine, along with minerals ringwoodite
Ringwoodite
Ringwoodite is a high-pressure polymorph of olivine, and it is stable at high temperatures and pressures like those in the Earth's mantle near 600 km depth. This mineral was first identified in the Tenham Meteorites in 1969, and it is inferred to be present in large quantity in the earth’s...
. Finally, wadsleyite was named after Dr. Arthur David Wadsley in his honor of his contributions to the field of geology.
Composition
Wadsleyite is a polymorph of forsteriteForsterite
Forsterite is the magnesium rich end-member of the olivine solid solution series. Forsterite crystallizes in the orthorhombic system with cell parameters a 4.75 Å , b 10.20 Å and c 5.98 Å .Forsterite is associated with igneous and metamorphic rocks and has also been found in meteorites...
Mg2SiO4, an end-member of the solid-solution series of olivine. (Horiuchi and Sawamoto, 1981) In the phase transformations of forsterite to fayalite
Fayalite
Fayalite is the iron-rich end-member of the olivine solid-solution series. In common with all minerals in the olivine group, fayalite crystallizes in the orthorhombic system with cell parameters a 4.82 Å, b 10.48 Å and c Å 6.09.Iron rich olivine is a relatively common constituent of acidic and...
Mg2SiO4-Fe2SiO4, this magnesium-rich olivine α-Mg2SiO4 changes to wadsleyite β-Mg2SiO4 under certain pressure and temperature conditions, and then with increasing pressure, it transforms to γ-Mg2SiO4 which is a spinel
Spinel
Spinel is the magnesium aluminium member of the larger spinel group of minerals. It has the formula MgAl2O4. Balas ruby is an old name for a rose-tinted variety.-Spinel group:...
structure. (Agrell, Price, Putnis and Smith, 1983) Wadsleyite is synthesized stably at 1400˚C and under 17GPa of pressure between depths of 410 and 660km. Figure 1 shows the high pressure phases of olivine
Olivine
The mineral olivine is a magnesium iron silicate with the formula 2SiO4. It is a common mineral in the Earth's subsurface but weathers quickly on the surface....
polymorphs beginning with wadsleyite β-Mg2SiO4. Geologically speaking, it is a very fine-grained “reactive” forsterite that had been synthesized from hydrous starting materials.
In values of weight percent oxide, the pure magnesian variety of wadsleyite would be 44.5% SiO2, 52.2% MgO, and 3.33% H2O. The average microprobe analysis for wadsleyite yielded: MgO 38.21, SiO2 38.7, CaO 0.07, Cr2O3 0.01, MnO 0.43, GeO 22.37, NiO 0.11 and ZnO 0.10. (Smyth, 1987) A recalculation of the number of cations on the basis of four oxygens will yield MgO 1.51, SiO2 1.03, CaO 0.0019, Cr2O3 0.0002, MnO 0.0096, GeO 0.4032, NiO 0.0023 and ZnO 0.0019.
An analysis of trace elements in wadsleyite suggests that there are a number of elements included in it. Results demonstrate traces of rubidium
Rubidium
Rubidium is a chemical element with the symbol Rb and atomic number 37. Rubidium is a soft, silvery-white metallic element of the alkali metal group. Its atomic mass is 85.4678. Elemental rubidium is highly reactive, with properties similar to those of other elements in group 1, such as very rapid...
Rb, strontium
Strontium
Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically. The metal turns yellow when exposed to air. It occurs naturally in the minerals celestine and...
Sr, barium
Barium
Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with...
Ba, titanium
Titanium
Titanium is a chemical element with the symbol Ti and atomic number 22. It has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver color....
Ti, zirconium
Zirconium
Zirconium is a chemical element with the symbol Zr and atomic number 40. The name of zirconium is taken from the mineral zircon. Its atomic mass is 91.224. It is a lustrous, grey-white, strong transition metal that resembles titanium...
Zr, niobium
Niobium
Niobium or columbium , is a chemical element with the symbol Nb and atomic number 41. It's a soft, grey, ductile transition metal, which is often found in the pyrochlore mineral, the main commercial source for niobium, and columbite...
Nb, hafnium
Hafnium
Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869. Hafnium was the penultimate stable...
Hf, tantalum
Tantalum
Tantalum is a chemical element with the symbol Ta and atomic number 73. Previously known as tantalium, the name comes from Tantalus, a character in Greek mythology. Tantalum is a rare, hard, blue-gray, lustrous transition metal that is highly corrosion resistant. It is part of the refractory...
Ta, thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
Th, and uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
U in wadsleyite relative to olivine. (Fujii, Mibe, Nakai and Orihashi, 2006) This information suggests that the concentrations of these elements could be larger than what has been supposed in the transition zone of Earth’s upper mantle. Moreover, these results help in understanding chemical differentiation and magmatism inside the Earth. (Fujii, Mibe, Nakai and Orihashi, 2006)
Geologic occurrence
Wadsleyite was found in Peace RiverPeace River (meteorite)
Peace River is a L6 chondrite meteorite fall on the morning of March 31, 1963.-History:On March 31, 1963 at 4:35 a.m. MST, a small meteoroid detonated at a height of 13 km over the skies of Alberta, Canada and broke in two main fragments...
meteorite
Meteorite
A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...
in Peace River, Alberta, Canada. This meteorite, an L6 hypersthene
Hypersthene
Hypersthene is a common rock-forming inosilicate mineral belonging to the group of orthorhombic pyroxenes. Many references have formally abandoned this term, preferring to categorise this mineral as enstatite or ferrosilite. It is found in igneous and some metamorphic rocks as well as in stony and...
-olivine chrondite, is believed to have formed during an extraterrestrial shock event on earth, beginning a solution-series of olivine. It occurs as microcrystalline rock fragments, often not surpassing 0.5mm in diameter, that pseudomorph
Pseudomorph
In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form , resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced by another...
pre-existing olivine parts within the mineral. (Agrell, Price, Putnis and Smith, 1983) To the left, Figure 2 shows a microcrystalline image of wadsleyite. The meteor or asteroid
Asteroid
Asteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
that impacted the earth generated the mineral phase transformations observed in shocked chrondites of the Peace River meteorite. (Beck, Gillet, Jahn, McMillan, Reynard, Van De Moortele and Wilson, 2007) It contains sulfide-rich veins of olivine and is believed, like other meteorite specimens, to have undergone a shock event, causing the grain components of olivine to transform into significant amounts of high-density wadsleyite. (Agrell, Price, Putnis and Smith, 1983)
Structure
Wasdsleyite’s structure is based on a somewhat distorted cubic-closest packing of oxygen atoms. The α-axis and the β-axis is the half diagonal of the spinel unit. The magnesiumMagnesium
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...
and 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...
are completely ordered in the structure. The hydrated O2 atom lies at the center of four edge-sharing Mg3+ octahedra. The compression of the unoccupied oxygen polyhedra plays a significant role in density increase of “pressure-induced” segments of transformations. (Smyth, 1994) This mineral contains three distinct tetrahedral sites, six different octahedral sites and eight distinct oxygen sites. (Kleppe, 2006) .The Mg3+ atoms occupy the octahedral sites; Si4+ atoms occupy the tetrahedral sites. Within the oxygen sites, some oxygens are unoccupied in the polyhedra, creating a shallow electrostatic potential for the mineral. (Horiuchi and Sawamoto, 1981)This meets the criteria for potential hydroxyl sites, in which the unoccupied oxygens become hydrated.
Wadsleyite is a pyrosilicate and a polymerized tetrahedral in which mostly Si2O7 groups are present. (Ashbrook, Berry, Farnanf, Le Polle, Pickard and Wimperise, 2006) A structure of β-Mg2SiO4 is shown in Figure 3. Wadsleyite II has both a single (SiO4) and coupled tetrahedral (Si2O7). It is a hydrous magnesium-iron silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
with variable composition that occurs between the stability regions of wadsleyite and ringwoodite
Ringwoodite
Ringwoodite is a high-pressure polymorph of olivine, and it is stable at high temperatures and pressures like those in the Earth's mantle near 600 km depth. This mineral was first identified in the Tenham Meteorites in 1969, and it is inferred to be present in large quantity in the earth’s...
γ-Mg2SiO4. (Kleppe, 2006) One-fifth of the silicon atom is in isolated tetrahedral and four-fifths is in Si2O7 groups so that the structure can be thought of as a mixture of one-fifth spinel and four-fifths wadsleyite. (Horiuchi and Sawamoto, 1981)
In the phase of wadsleyite II, there is considered to be possible host hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
in the transition zone of the Earth’s mantle. Since forsterite is thought to be about or little over 50% of the mantle, the transition region in the upper mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....
could be an important water reservoir. (Kleppe, 2006) Wadsleyite is very water soluble and can accept up to 3 wt. % H2O as hydroxyl
Hydroxyl
A hydroxyl is a chemical group containing an oxygen atom covalently bonded with a hydrogen atom. In inorganic chemistry, the hydroxyl group is known as the hydroxide ion, and scientists and reference works generally use these different terms though they refer to the same chemical structure in...
at this site. Its water content is very significant in understanding the way Earth developed. Synthetic hydrous wadsleyite II is pictured in Figure 4. Wadsleyite II in a variably hydrous magnesium-iron silicate
Silicate
A silicate is a compound containing a silicon bearing anion. The great majority of silicates are oxides, but hexafluorosilicate and other anions are also included. This article focuses mainly on the Si-O anions. Silicates comprise the majority of the earth's crust, as well as the other...
phase. It is a potential host for hydrogen in the transition zone of the Earth's mantle. However, if the water composition of wadsleyite surpasses a 0.1–0.2 wt% amount, it could cause partial melting. As a result, an upwelling flow of water could affect the distribution of particular elements in the Earth. (Huang, Karato and Xu, 2005)
Physical properties
As an orthorhombic crystal system, wadsleyite’s unit cell volume is V 550.00Ǻ³. Its space group is Imma and its cell parameters are as follows: a = 5.6921Ǻ, b = 11.46Ǻ and c = 8.253Ǻ. (Agrell, Price, Putnis and Smith, 1983) A more recent structure of wadsleyite confirms the cell parameters to be a = 5.698Ǻ, b = 11.438Ǻ and c = 8.257Ǻ. (Horiuchi and Sawamoto, 1981) The condition of its diaphaneity is transparent and its color is light gray to light blue. As shown in the illustrations, Figure 5a shows wadsleyite in its purest state whereas Figure 5b shows a variety of samples of wadsleyite from pure to impure, clear to midnight blue.The wadsleyite minerals generally have a felsitic texture and are fractured. Because of small crystal size, detailed optical data could not be obtained; however, wadsleyite is anisotropic with low first-order 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...
colors. (Agrell, Price, Putnis and Smith, 1983) Its mean refractive index
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....
is n = 1.76, D = 3.84 and it is biaxial. In X-ray powder diffraction
Powder diffraction
Powder diffraction is a scientific technique using X-ray, neutron, or electron diffraction on powder or microcrystalline samples for structural characterization of materials.-Explanation:...
, its strongest points in pattern are: 2.886(50)(040), 2.691(40)(013), 2.452(100,141), 2.038(80)(240), 1.442(80)(244). (Agrell, Price, Putnis and Smith, 1983)
Biographic sketch
Late Dr. A. D. Wadsley received the privilege of getting a mineral named after him due his contributions to geology such as the crystallographyCrystallography
Crystallography is the experimental science of the arrangement of atoms in solids. The word "crystallography" derives from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and grapho = write.Before the development of...
of minerals and other inorganic compounds. (Agrell, Price, Putnis and Smith, 1983) His impressive investigations of minerals were all known to the mass in his field and to many others in the studies of geology. The proposal to have Wadsleyite named after Wadsley was approved by the Commission on New Minerals and Mineral Names of the International Mineralogical Association
International Mineralogical Association
The International Mineralogical Association is an international group of 38 national societies. The goal is to promote the science of mineralogy and to standardize the nomenclature of the 4000 plus known mineral species...
. (Agrell, Price, Putnis and Smith, 1983) It is now preserved as an official mineral specimen in the Department of Geology’s collection at the University of Alberta. Dr. Wadsley accepted this honor for his exceptional knowledge in the geologic field of study.