syenite


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Related to syenite: trachyte

syenite

(sī`ənīt), coarse-grained igneous rockrock,
aggregation of solid matter composed of one or more of the minerals forming the earth's crust. The scientific study of rocks is called petrology. Rocks are commonly divided, according to their origin, into three major classes—igneous, sedimentary, and metamorphic.
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, similar in appearance and composition to granite. Unlike granite, it contains little or no quartz. The chief minerals in syenite are the feldspars, with mica, hornblende, and pyroxene. Varieties are distinguished (according to the ferromagnesian minerals contained) as augite syenite, hornblende syenite, mica syenite, and nepheline syenite. Syenites are comparatively rare rocks, being found chiefly in a few areas of the United States and Germany. They are occasionally substituted for granites as building stones.

Syenite

 

a holocrystalline plutonic rock composed chiefly of orthoclase and plagioclase, with admixtures of the following ferrous minerals: hornblende, biotite, pyroxene, and, occasionally olivine. Quartz is also sometimes present.

Depending on the content of ferrous minerals, syenite is classified as hornblende syenite, micaceous syenite, quartz syenite, and so forth. Syenite is characterized chemically by a silica content of 55 to 65 percent; the alkali content determines the classification of syenite into normal and alkali types. In normal syenites plagioclases are present as oligoclase and andesite. Alkali syenites contain orthoclase and, more rarely, albite. Nephelines or other feldspathoids, such as leucite and the so-dalite group of minerals, are formed when the alkali content exceeds 12 percent and the silica content is reduced; alkali syenites thus grade into nepheline syenites or other feldspathoid syenites. Monzonites or gabbro syenites are similar to syenites. They are composed of labradorite and orthoclase with admixtures of ferrous minerals, such as pyroxene.

In the USSR, syenites are abundant in the southern Ukraine (Volyn’ Oblast), the Urals, Kazakhstan, the Caucasus, and Middle Asia, where monzonites are found. Syenites are used for the same purposes as granites.

syenite

[′sī·ə‚nīt]
(petrology)
A visibly crystalline plutonic rock with granular texture composed largely of alkali feldspar, with subordinate plagioclose and mafic minerals; the intrusive equivalent of trachyte.
References in periodicals archive ?
The weight ratio of silica sand to Nepheline Syenite was maintained as the PVC varied.
The mineralogical characterization of the rocks biotite, syenite and argillite, with identification of their respective minerals, is described below (Figure 1).
Although the unusual rocks near Litchfield, Maine, had been known to mineral collectors for decades prior, Clarke (1886) provided the first detailed mineralogical descriptions of nepheline syenite from the Litchfield pluton.
The Khibiny Massif is a famous and unique mineral locality that is composed of a nepheline syenite intrusion rich in a large number of rare minerals.
Among the additives options that prevent thin plastic layers from sticking to each other, 'Talc, nepheline syenite, and DE have been the incumbent high-performance antiblock minerals in plastic films," says John Flurley, president and CEO of Trinity Resources.
distributor is Maroon Group, Avon, Ohio) is said to combine the best attributes of talc, nepheline syenite (NS), and diatomaceous earth (DE).
Bauxite is found in wide variety of rocks including syenite basalt limestone and schist [1].
Other resources are Nepheline Syenite, phosphates, gemstones, and metallic minerals including gold and base metals and variety of other industrial minerals.
1 to 5 parts per hundred parts resin (phr) of one or more wax and from 75 phr to 200 phr of one or more extenders wherein the one or more extenders is selected from the group consisting of barium sulfate, titanium dioxide, iron oxides, crystalline silica (quartz), calcium metasilicate, soda lime glass spheres, magnesium silicate, nepheline syenite, muscovite mica, diatomaceous earth, kaolin clay and calcium carbonate.