Gonnardite
Encyclopedia
Gonnardite is a comparatively rare, fibrous zeolite
, natrolite
subgroup. Older papers claim that a complete solid solution exists between tetranatrolite and gonnardite, but tetranatrolite was discredited as a separate species in 1999. A series, based on the disorder of the silicon-aluminum in the framework, appears to exist between Na-rich gonnardite and natrolite, Na2(Si3Al2)O10·2H2O.
Gonnardite was named in 1896 after Ferdinand Pierre Joseph Gonnard (1833–1923), who was Professor of Mining Engineering at the University of Lyon, France.
Unit Cell Parameters: a = b = 13.21 Å, c = 6.622 Å, Z = 2
Space Group: I2d
, bounded by {110} and {111} as well as {100} and {001}, and gonnardite also occurs as radial hemispheres. Commonly found as zoned prisms or aggregates with thomsonite
, natrolite
and paranatrolite.
, calcium
or barium
, together with oxygen and water. Gonnardite has the same framework structure as natrolite, but a disordered Si, Al distribution on the tetrahedral sites. Some of the water sites in the disordered natrolite structure of gonnardite are empty.
and natrolite
in vesicle
s in the volcanic rock
of The Nut, near Stanley, Tasmania
, Australia, intergrown with natrolite
at Don Hill, Tasmania and in drill holes with chabazite
and calcite
near Guildford, Tasmania. It is also found in nepheline-syenite in the Grenville Geological Province
, which is part of the Canadian Shield
.
The type locality
(the place where the mineral was first described) is La Chaux de Bergonne, Gignat
, Saint-Germain-Lembron, Puy-de-Dôme, Auvergne
, France, and type material from this locality is held at the Natural History Museum, London, England, registration number BM.1930,166.
Zeolite
Zeolites are microporous, aluminosilicate minerals commonly used as commercial adsorbents. The term zeolite was originally coined in 1756 by Swedish mineralogist Axel Fredrik Cronstedt, who observed that upon rapidly heating the material stilbite, it produced large amounts of steam from water that...
, natrolite
Natrolite
Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula . The type locality is Hohentwiel, Hegau, Germany....
subgroup. Older papers claim that a complete solid solution exists between tetranatrolite and gonnardite, but tetranatrolite was discredited as a separate species in 1999. A series, based on the disorder of the silicon-aluminum in the framework, appears to exist between Na-rich gonnardite and natrolite, Na2(Si3Al2)O10·2H2O.
Gonnardite was named in 1896 after Ferdinand Pierre Joseph Gonnard (1833–1923), who was Professor of Mining Engineering at the University of Lyon, France.
Crystallography
Orthorhombic-bipyramidal class 2/m 2/m 2/m and tetragonal-scalenoidal class 2m (orthorhombic with a very close to b, or tetragonal with a equal to b).Unit Cell Parameters: a = b = 13.21 Å, c = 6.622 Å, Z = 2
Space Group: I2d
Crystal habit
Crystals are prismaticPrism (geometry)
In geometry, a prism is a polyhedron with an n-sided polygonal base, a translated copy , and n other faces joining corresponding sides of the two bases. All cross-sections parallel to the base faces are the same. Prisms are named for their base, so a prism with a pentagonal base is called a...
, bounded by {110} and {111} as well as {100} and {001}, and gonnardite also occurs as radial hemispheres. Commonly found as zoned prisms or aggregates with thomsonite
Thomsonite
Thomsonite is the name of a series of tecto-silicate minerals of the zeolite group. Prior to 1997, thomsonite was recognized as a mineral species, but a reclassification in 1997 by the International Mineralogical Association changed it to a series name, with the mineral species being named...
, natrolite
Natrolite
Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula . The type locality is Hohentwiel, Hegau, Germany....
and paranatrolite.
Structure
Gonnardite is a tectosilicate belonging to the natrolite group. The natrolite minerals are composed of chains of AlO4 and SiO4 tetrahedra that link to form frameworks. As with all zeolites, there are channels within the framework, and for the natrolite minerals the channels are occupied by polyhedra containing sodiumSodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
, 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...
or 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...
, together with oxygen and water. Gonnardite has the same framework structure as natrolite, but a disordered Si, Al distribution on the tetrahedral sites. Some of the water sites in the disordered natrolite structure of gonnardite are empty.
Environment
Gonnardite has been found in silica-poor volcanics and pegmatites. It occurs with thomsoniteThomsonite
Thomsonite is the name of a series of tecto-silicate minerals of the zeolite group. Prior to 1997, thomsonite was recognized as a mineral species, but a reclassification in 1997 by the International Mineralogical Association changed it to a series name, with the mineral species being named...
and natrolite
Natrolite
Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula . The type locality is Hohentwiel, Hegau, Germany....
in vesicle
Vesicular texture
Vesicular texture is a volcanic rock texture characterised by a rock being pitted with many cavities at its surface and inside. The texture is often found in extrusive aphanitic, or glassy, igneous rock...
s in the volcanic rock
Volcanic rock
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...
of The Nut, near Stanley, Tasmania
Stanley, Tasmania
Stanley is a town on the north-west coast of Tasmania, Australia. Travelling west, Stanley is the second-last major township on the north-west coast of Tasmania, Smithton being the larger township in the Circular Head municipality...
, Australia, intergrown with natrolite
Natrolite
Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula . The type locality is Hohentwiel, Hegau, Germany....
at Don Hill, Tasmania and in drill holes with chabazite
Chabazite
Chabazite is a tectosilicate mineral of the zeolite group, closely related to gmelinite, with formula Al2Si4O12·6H2O. Recognized varieties include Chabazite-Ca, Chabazite-K, Chabazite-Na, and Chabazite-Sr, depending on the prominence of the indicated cation.Chabazite crystallizes in the triclinic...
and 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:...
near Guildford, Tasmania. It is also found in nepheline-syenite in the Grenville Geological Province
Grenville orogeny
The Grenville Orogeny was a long-lived Mesoproterozoic mountain-building event associated with the assembly of the supercontinent Rodinia. Its record is a prominent orogenic belt which spans a significant portion of the North American continent, from Labrador to Mexico, as well as to Scotland...
, which is part of the Canadian Shield
Canadian Shield
The Canadian Shield, also called the Laurentian Plateau, or Bouclier Canadien , is a vast geological shield covered by a thin layer of soil that forms the nucleus of the North American or Laurentia craton. It is an area mostly composed of igneous rock which relates to its long volcanic history...
.
The type locality
Type 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....
(the place where the mineral was first described) is La Chaux de Bergonne, Gignat
Gignat
Gignat is a commune in the Puy-de-Dôme department in Auvergne in central France.-References:*...
, Saint-Germain-Lembron, Puy-de-Dôme, Auvergne
Auvergne (région)
Auvergne is one of the 27 administrative regions of France. It comprises the 4 departments of Allier, Puy de Dome, Cantal and Haute Loire.The current administrative region of Auvergne is larger than the historical province of Auvergne, and includes provinces and areas that historically were not...
, France, and type material from this locality is held at the Natural History Museum, London, England, registration number BM.1930,166.