Jennite - AbsoluteAstronomy.com

Jennite is a calcium silicate hydrate

Calcium silicate hydrate

Calcium Silicate Hydrate is the main product of the hydration of Portland cement and is primarily responsible for the strength in cement based materials.-Preparation:...

(CSH) of general chemical formula: Ca₉Si₆O₁₈(OH)₆·8(H₂O).

Jennite occurs in hydrated cement

Cement

In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...

paste and can be found in nature in particular conditions, e.g., as alteration mineral in metamorphosed

Metamorphism

Metamorphism is the solid-state recrystallization of pre-existing rocks due to changes in physical and chemical conditions, primarily heat, pressure, and the introduction of chemically active fluids. Mineralogical, chemical and crystallographic changes can occur during this process...

limestone

Limestone

Limestone is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate . Many limestones are composed from skeletal fragments of marine organisms such as coral or foraminifera....

and skarn

Skarn

Skarn 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...

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A first specimen of jennite found in 1966 at the Crestmore quarries (Crestmore, 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,...

, USA) was analysed and identified as a new mineral by Carpenter in 1966 (Carpenter, 1966). They named it in honour of its discoverer: Clarence Marvin Jenni (1896–1973) director of the Geological Museum at the University of Missouri

University of Missouri

The University of Missouri System is a state university system providing centralized administration for four universities, a health care system, an extension program, five research and technology parks, and a publishing press. More than 64,000 students are currently enrolled at its four campuses...

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In contrast to the first analysis made by Carpenter, jennite does not contain appreciable amount of sodium when the Crestmore specimen was reexamined (Gard, 1977).

The structure of jennite determined by is made of three distinct modules: ribbons of edge-sharing 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...

octahedra, silicate chains of wollastonite

Wollastonite

Wollastonite is a calcium inosilicate mineral that may contain small amounts of iron, magnesium, and manganese substituting for calcium. It is usually white. It forms when impure limestone or dolostone is subjected to high temperature and pressure sometimes in the presence of silica-bearing fluids...

-type running along the b axis, and additional calcium octahedra on inversion center

Symmetry operation

In the context of molecular symmetry, a symmetry operation may be defined as a permutation of atoms such that the molecule or crystal is transformed into a state indistinguishable from the starting state....

s. The 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...

groups are bonded to three calcium cations while no SiOH groups are observed (Bonaccorsi 2004).

Jennite transforms to metajennite at 70 – 90 °C by losing four water molecules.

See also