Minerals



A mineral is a naturally occurring substance that is solid and stable at room temperature, representable by a chemical formula, usually abiogenic, and has an ordered atomic structure. It is different from a rock, which can be an aggregate of minerals or non-minerals and does not have a specific chemical composition. The exact definition of a mineral is under debate, especially with respect to the requirement a valid species be abiogenic, and to a lesser extent with regards to it having an ordered atomic structure. The study of minerals is called mineralogy.

There are over 4,900 known mineral species; over 4,660 of these have been approved by the International Mineralogical Association (IMA). The silicate minerals compose over 90% of the Earth's crust. The diversity and abundance of mineral species is controlled by the Earth's chemistry. Silicon and oxygen constitute approximately 75% of the Earth's crust, which translates directly into the predominance of silicate minerals. Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish various species, and these properties in turn are influenced by the mineral's geological environment of formation. Changes in the temperature, pressure, and bulk composition of a rock mass cause changes in its mineralogy; however, a rock can maintain its bulk composition, but as long as temperature and pressure change, its mineralogy can change as well.

Minerals can be described by various physical properties which relate to their chemical structure and composition. Common distinguishing characteristics include crystal structure and habit, hardness, luster, diaphaneity, color, streak, tenacity, cleavage, fracture, parting, and specific gravity. More specific tests for minerals include reaction to acid, magnetism, taste or smell, and radioactivity.

Minerals are classified by key chemical constituents; the two dominant systems are the Dana classification and the Strunz classification. The silicate class of minerals is subdivided into six subclasses by the degree of polymerization in the chemical structure. All silicate minerals have a base unit of a [SiO4]4- silica tetrahedra - that is, a silicon cation coordinated by four oxygen anions, which gives the shape of a tetrahedron. These tetrahedra can be polymerized to give the subclasses: orthosilicates (no polymerization, thus single tetrahedra), disilicates (two tetrahedra bonded together), cyclosilicates (rings of tetrahedra), inosilicates (chains of tetrahedra), phyllosilicates (sheets of tetrahedra), and tectosilicates (three-dimensional network of tetrahedra). Other important mineral groups include the native elements, sulfides, oxides, halides, carbonates, sulfates, and phosphates. Read more ...




In the News ...





Rare Mineral Discovered in Ancient Meteorite Impact Crater   Live Science - November 3, 2014
A rare mineral known from just three massive meteorite impacts has now turned up in a Wisconsin crater. Researchers discovered the mineral, called reidite, at the Rock Elm impact structure in western Wisconsin. Reidite is a dense form of zircon, one of the hardiest minerals on Earth. This is the oldest reidite ever found,, said Aaron Cavosie, a geochemist at the University of Puerto Rico in Mayaguez. The Rock Elm meteorite crater is 450 million to 470 million years old, he said.




Earth's Most Abundant, But Hidden Mineral Finally Seen, Named   Live Science - June 16, 2014

Earth's most abundant mineral lies deep in the planet's interior, sealed off from human eyes. Now, scientists for the first time have gotten a glimpse of the rock, enclosed inside a 4.5-billion-year-old meteorite. The result: They have characterized and named the elusive mineral. The new official name, bridgmanite, was approved for the rock formerly known by its chemical components - silicate-perovskite. The magnesium-silicate mineral was named after Percy Bridgman, a 1946 Nobel Prize-winning physicist.




Mineral hints at bright blue rocks deep in the Earth   BBC - March 12, 2014

Minerals preserved in diamond have revealed hints of the bright blue rocks that exist deep within the Earth.They also provide the first direct evidence that there may be as much water trapped in those rocks as there is in all the oceans. The diamond, from central-west Brazil, contains minerals that formed as deep as 600km down and that have significant amounts of water trapped within them.




Rare Diamond Reveals Earth's Interior is All Wet   Live Science - March 12, 2014

A battered diamond that survived a trip from "hell" confirms a long-held theory: Earth's mantle holds an ocean's worth of water. "It's actually the confirmation that there is a very, very large amount of water that's trapped in a really distinct layer in the deep Earth," said Graham Pearson, lead study author and a geochemist at the University of Alberta in Canada. The worthless-looking diamond encloses a tiny piece of an olivine mineral called ringwoodite, and it's the first time the mineral has been found on Earth's surface in anything other than meteorites or laboratories. Ringwoodite only forms under extreme pressure, such as the crushing load about 320 miles (515 kilometers) deep in the mantle.




4.5-Billion-Year-Old Antarctic Meteorite Yields New Mineral   Live Science - April 6, 2011

A meteorite discovered in Antarctica in 1969 has just divulged a modern secret: a new mineral, now called Wassonite. The new mineral found in the 4.5-billion-year-old meteorite was tiny - less than one-hundredth as wide as a human hair. Still, that was enough to excite the researchers who announced the discovery Tuesday (April 5).




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