Donnayite-(Y)
Encyclopedia
Donnayite- is a rare earth
carbonate
consisting of the rare earth metal yttrium
. It was first discovered in 1978 at Mont St-Hilaire, Quebec
. Donnayite was subsequently identified and named after Joseph D.H. Donnay and his wife, Gabrielle Donnay. Both were prominent mineralogists and crystallographers, and J.D.H. Donnay was awarded the Roebling Award by the Mineralogical Society of America
in 1971 for his emphasis on the importance of optical mineralogy
and crystal morphology. Donnayite tends to occur in small quantities in the pegmatite
dykes and miarolitic cavities of mountainous regions. It crystallizes in this environment with increasing alkalinity values until the alkalinity suddenly drops during the last stage of crystallization
. This results in increasing amounts of Na carbonates and REE minerals. First discovered at Mont St-Hilaire, donnayite has since been found in the Southern Ural Mountains of Russia and the Narssarssuk pegmatite of South Greenland. Donnayite crystals tend to be small and the color is commonly pale yellow to yellow with a white streak
and a vitreous luster. Donnayite crystals usually display trigonal or hexagonal symmetry and have a hardness of 3. Twinning
is extremely common in this mineral. Minerals closely related to donnayite include synchysite, calcite, sphalerite, microcline, and analcime. Donnayite is isomorphous with weloganite and mckelveyite.
). Generally speaking, mineral hydration
occurs when water is added to the structure of the mineral, which occurs in retrograde metamorphism (when temperatures during crystallization suddenly drop, and H activity increases). Donnayite was first analyzed using a Cambridge MK5 electron microprobe
. Electron microprobe analysis of donnayite in 1978 yielded the following weight percent oxides (Baker et al., 1978):
The CO2 and H2O values given were calculated on the basis of 6(CO3)-2 and 3(H2O) per formula by comparison with weloganite.
atom is bonded to 10 oxygen atoms. Donnayite has a structure very similar to shomiokite-(Y). The Na(CO3)∙H2O of shomiokite are cross-linked through the layers of Y polyhedra which results in ‘mixed’ carbonate layers. In this ‘mixed’ layer, the CO3 triangles are tilted within the layer which allows the H2O groups and Na octahedral to share the slab with the CO2 polyhedra. The (Na, Y)CO3∙H2O layer of donnayite is comparable to this. However, the Sr atoms of donnayite have 9-fold coordination with an extra layer of flat-lying carbonate groups. This is shown in the figure below. In the structure of the REE carbonate, donnayite, the effects of H-bonding are negligible.
on the c-axis {001}. Donnayite crystals usually display trigonal or hexagonal symmetry and belong to the point group
1 or 3m and the space group P1. Optically, donnayite is biaxial negative with a 2v (measured) ranging from 0ᵒ-30ᵒ.
syenite
s at Mont St-Hilaire, Quebec. It is usually found in rocks from the alkaline complexes and in carbonatites. During crystallization of the nepheline syenite, the alkalinity
continues to increase until the very last stage, when the alkalinity suddenly drops, resulting in decreasing temperature
and an increase in H activity. This is exemplified by increasing amounts of Na carbonates and REE minerals. In addition, during the last stages of crystallization in more acidic conditions, minerals form with increasing amounts of H2O, and REE minerals rich in Y. In 1973, donnayite was first discovered at Mont St-Hilaire, but was incorrectly identified as ‘brockite.’ Finally, in 1978 it became possible to gather sufficient data to characterize this sample as the new species, donnayite. In addition to this geologic occurrence, donnayite can be found in Russia at Mt. Kukisvumchorr, Khibiny massif
, Kola Peninsula
, and at the Vishnevogorsk complex, Vishnevy-Ilmen Mountains, Southern Ural Mountains
. Recently, donnayite has been discovered along with ewaldite, epitaxially intergrown, in crystals from the Narssarssuk
pegmatite in South Greenland. Related minerals include ewaldite, mckelveyite
, synchysite, calcite
, sphalerite
, microcline, and analcime.
, as an essential constituent. Although donnayite has no known human uses, it has other characteristics that make it distinct and for this reason most people do not even know this mineral exists.
and mineralogist, and professor at John Hopkins University. He served as president of the Mineralogical Society of America and in 1971 was awarded its highest honor, the Roebling Medal. Donnay emphasized the importance of optical mineralogy and crystal morphology and how they related to crystal structure
. He is the author of 100 abstracts, 148 papers, 36 books (or chapters in books), 38 reviews, and several non-scientific papers. His wife, Dr. Gabrielle Donnay was a professor of crystallography at McGill University
in Montreal, Canada where Dr. J.D.H. Donnay later became Research Associate and a guest professor.
Rare earth
Rare earth may refer to:* Rare earth elements, a group of elements on the periodic table* Rare earth mineral, a mineral substantively composed of these elements* Rare-earth magnet, a type of magnet that employs rare earth elements to increase effectiveness...
carbonate
Carbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
consisting of the rare earth metal yttrium
Yttrium
Yttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and it has often been classified as a "rare earth element". Yttrium is almost always found combined with the lanthanides in rare earth minerals and is...
. It was first discovered in 1978 at Mont St-Hilaire, Quebec
Quebec
Quebec or is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking population and the only one whose sole official language is French at the provincial level....
. Donnayite was subsequently identified and named after Joseph D.H. Donnay and his wife, Gabrielle Donnay. Both were prominent mineralogists and crystallographers, and J.D.H. Donnay was awarded the Roebling Award by the Mineralogical Society of America
Mineralogical Society of America
The Mineralogical Society of America is a scientific membership organization. MSA was founded in 1919 for the advancement of mineralogy, crystallography, geochemistry, and petrology, and promotion of their uses in other sciences, industry, and the arts...
in 1971 for his emphasis on the importance of optical mineralogy
Optical mineralogy
Optical mineralogy is the study of minerals and rocks by measuring their optical properties. Most commonly, rock and mineral samples are prepared as thin sections or grain mounts for study in the laboratory with a petrographic microscope...
and crystal morphology. Donnayite tends to occur in small quantities in the pegmatite
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....
dykes and miarolitic cavities of mountainous regions. It crystallizes in this environment with increasing alkalinity values until the alkalinity suddenly drops during the last stage of crystallization
Crystallization
Crystallization is the process of formation of solid crystals precipitating from a solution, melt or more rarely deposited directly from a gas. Crystallization is also a chemical solid–liquid separation technique, in which mass transfer of a solute from the liquid solution to a pure solid...
. This results in increasing amounts of Na carbonates and REE minerals. First discovered at Mont St-Hilaire, donnayite has since been found in the Southern Ural Mountains of Russia and the Narssarssuk pegmatite of South Greenland. Donnayite crystals tend to be small and the color is commonly pale yellow to yellow with a white streak
Streak
Streak or streaking may refer to:*Streaking, running naked in a public place*Streaking , a method of purifying micro-organisms*Streak , the color left by a mineral dragged across a rough surface...
and a vitreous luster. Donnayite crystals usually display trigonal or hexagonal symmetry and have a hardness of 3. Twinning
Twinning
Twinning may refer to:* In biology and agriculture, producing two offspring at a time, or having a tendency to do so;* Twin towns and sister cities, towns and cities involved in town twinning...
is extremely common in this mineral. Minerals closely related to donnayite include synchysite, calcite, sphalerite, microcline, and analcime. Donnayite is isomorphous with weloganite and mckelveyite.
Composition
The chemical formula of donnayite is: NaCaSr3Y(CO3)6∙3H2O. Donnayite is comprised of the cations sodium, calcium, strontium, and yttrium. Of these cations, strontium and yttrium are the most prominent. In addition to this, donnayite contains a significant amount of water, making it a hydrated mineral (more specifically, a hydrated carbonateCarbonate
In chemistry, a carbonate is a salt of carbonic acid, characterized by the presence of the carbonate ion, . The name may also mean an ester of carbonic acid, an organic compound containing the carbonate group C2....
). Generally speaking, mineral hydration
Mineral hydration
Mineral hydration is an inorganic chemical reaction where water is added to the crystal structure of a mineral, usually creating a new mineral, usually called a hydrate....
occurs when water is added to the structure of the mineral, which occurs in retrograde metamorphism (when temperatures during crystallization suddenly drop, and H activity increases). Donnayite was first analyzed using a Cambridge MK5 electron microprobe
Electron microprobe
An electron microprobe , also known as an electron probe microanalyzer or electron micro probe analyzer , is an analytical tool used to non-destructively determine the chemical composition of small volumes of solid materials...
. Electron microprobe analysis of donnayite in 1978 yielded the following weight percent oxides (Baker et al., 1978):
| Oxide | Weight % |
|---|---|
| Na2O | 3.37 |
| CaO | 5.75 |
| BaO | 0.85 |
| SrO | 35.8 |
| Y2O3 | 13.1 |
| Nd2O3 | 1.83 |
| La2O3 | 0.45 |
| CO2 | 30.98 |
| H2O | 6.34 |
| Total | 98.47 |
The CO2 and H2O values given were calculated on the basis of 6(CO3)-2 and 3(H2O) per formula by comparison with weloganite.
Structure
Donnayite consists of six carbonate anions, together with three H2O molecules. The asymmetric unit contains three independent sites occupied by Sr and three additional sites which are occupied by Na+, Ca2+, or Y3+. Each strontiumStrontium
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...
atom is bonded to 10 oxygen atoms. Donnayite has a structure very similar to shomiokite-(Y). The Na(CO3)∙H2O of shomiokite are cross-linked through the layers of Y polyhedra which results in ‘mixed’ carbonate layers. In this ‘mixed’ layer, the CO3 triangles are tilted within the layer which allows the H2O groups and Na octahedral to share the slab with the CO2 polyhedra. The (Na, Y)CO3∙H2O layer of donnayite is comparable to this. However, the Sr atoms of donnayite have 9-fold coordination with an extra layer of flat-lying carbonate groups. This is shown in the figure below. In the structure of the REE carbonate, donnayite, the effects of H-bonding are negligible.
Physical properties
Typical donnayite crystals are very small, ranging from 0.05 to 1.0 mm, and rarely reaching 2.0 mm. Donnayite is commonly pale yellow to yellow, but can also be colorless, white, gray, and very rarely, reddish brown, due to hematite inclusions. The streak of this mineral is white and it has a vitreous luster. Donnayite ranks at a hardness of 3 on Moh’s scale and has fair to imperfect cleavageCleavage
Cleavage may refer to:*Cleavage , partial exposure of the separation between a woman's breasts.**Cleavage enhancement, methods of making a person's breast cleavage look more substantial than it really is....
on the c-axis {001}. Donnayite crystals usually display trigonal or hexagonal symmetry and belong to the 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...
1 or 3m and the space group P1. Optically, donnayite is biaxial negative with a 2v (measured) ranging from 0ᵒ-30ᵒ.
| Color | Yellow |
| Streak | White |
| Luster | Vitreous |
| Hardness | 3 |
| Cleavage | {001} |
| Symmetry | Trigonal/Hexagonal |
| Point Group | 1 or 3m |
Geologic occurrence
Donnayite occurs in minute quantities in the pegmatite dykes, miarolitic cavities, and interstices in the nephelineNepheline
Nepheline, also called nephelite , is a feldspathoid: a silica-undersaturated aluminosilicate, Na3KAl4Si4O16, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatites...
syenite
Syenite
Syenite is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or present in relatively small amounts Syenite is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or...
s at Mont St-Hilaire, Quebec. It is usually found in rocks from the alkaline complexes and in carbonatites. During crystallization of the nepheline syenite, the alkalinity
Alkalinity
Alkalinity or AT measures the ability of a solution to neutralize acids to the equivalence point of carbonate or bicarbonate. The alkalinity is equal to the stoichiometric sum of the bases in solution...
continues to increase until the very last stage, when the alkalinity suddenly drops, resulting in decreasing temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
and an increase in H activity. This is exemplified by increasing amounts of Na carbonates and REE minerals. In addition, during the last stages of crystallization in more acidic conditions, minerals form with increasing amounts of H2O, and REE minerals rich in Y. In 1973, donnayite was first discovered at Mont St-Hilaire, but was incorrectly identified as ‘brockite.’ Finally, in 1978 it became possible to gather sufficient data to characterize this sample as the new species, donnayite. In addition to this geologic occurrence, donnayite can be found in Russia at Mt. Kukisvumchorr, Khibiny massif
Khibiny Massif
The Khibiny Massif, Khibiny Mountains, Khibinsky Mountains or Khibins, Khibinsky tundras, Khibiny is one of the two main mountain ranges of the Kola Peninsula, Russia, within the Arctic Circle, located between Imandra and Umbozero lakes.The massif is of oval shape of about 1,300 sq.km...
, Kola Peninsula
Kola Peninsula
The Kola Peninsula is a peninsula in the far northwest of Russia. Constituting the bulk of the territory of Murmansk Oblast, it lies almost completely to the north of the Arctic Circle and is washed by the Barents Sea in the north and the White Sea in the east and southeast...
, and at the Vishnevogorsk complex, Vishnevy-Ilmen Mountains, Southern Ural Mountains
Ural Mountains
The Ural Mountains , or simply the Urals, are a mountain range that runs approximately from north to south through western Russia, from the coast of the Arctic Ocean to the Ural River and northwestern Kazakhstan. Their eastern side is usually considered the natural boundary between Europe and Asia...
. Recently, donnayite has been discovered along with ewaldite, epitaxially intergrown, in crystals from the Narssarssuk
Narssârssuk
Narsaarsuk is an abandoned settlement on the edge of Bylot Sound in northern Greenland near Thule Air Base. The site of the former settlement is contaminated with plutonium after the 1968 Thule Air Base B-52 crash....
pegmatite in South Greenland. Related minerals include ewaldite, mckelveyite
McKelveyite
Mckelveyite is a hydrated sodium, barium, yttrium, and uranium–containing carbonate, with the chemical formula 36. It was first described in 1965 from deposits in the Green River Formation, Sweetwater County, Wyoming, and is named after Vincent Ellis McKelvey , a former director of the United...
, synchysite, calcite
Calcite
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite. Aragonite will change to calcite at 380-470°C, and vaterite is even less stable.-Properties:...
, sphalerite
Sphalerite
Sphalerite is a mineral that is the chief ore of zinc. It consists largely of zinc sulfide in crystalline form but almost always contains variable iron. When iron content is high it is an opaque black variety, marmatite. It is usually found in association with galena, pyrite, and other sulfides...
, microcline, and analcime.
Special characteristics
As of today, donnayite has no real historical or political significance. There are no common uses for this mineral, and it is not used for the fabrication of any known products. The characteristics that make donnayite special are its small size, and the few locations on Earth at which this mineral can be found. It requires a unique environment to form and crystallize, and for this reason donnayite has only been found in three countries of the world. Another characteristic that makes donnayite unique is the fact that it contains the REE, yttriumYttrium
Yttrium is a chemical element with symbol Y and atomic number 39. It is a silvery-metallic transition metal chemically similar to the lanthanides and it has often been classified as a "rare earth element". Yttrium is almost always found combined with the lanthanides in rare earth minerals and is...
, as an essential constituent. Although donnayite has no known human uses, it has other characteristics that make it distinct and for this reason most people do not even know this mineral exists.
Name
Donnayite was named in honor of Joseph Desire Hubert Donnay, and his wife, Gabrielle Donnay (Baker et al., 1978). J.D.H. Donnay (1902-1994) was an accomplished Belgian-American-Canadian crystallographerCrystallographer
Crystallographer could refer to someone who practices:*X-ray crystallography*Crystallography...
and mineralogist, and professor at John Hopkins University. He served as president of the Mineralogical Society of America and in 1971 was awarded its highest honor, the Roebling Medal. Donnay emphasized the importance of optical mineralogy and crystal morphology and how they related to crystal structure
Crystal 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...
. He is the author of 100 abstracts, 148 papers, 36 books (or chapters in books), 38 reviews, and several non-scientific papers. His wife, Dr. Gabrielle Donnay was a professor of crystallography at McGill University
McGill University
Mohammed Fathy is a public research university located in Montreal, Quebec, Canada. The university bears the name of James McGill, a prominent Montreal merchant from Glasgow, Scotland, whose bequest formed the beginning of the university...
in Montreal, Canada where Dr. J.D.H. Donnay later became Research Associate and a guest professor.