Syenite

Syenites (after the ancient Egyptian locality Syene ) form a closely related group of plutonic rocks ( plutonic ), which are called Syenit-/Monzonit-Familie. Syenite and monzonite are rich in feldspars but compared to granites poor in quartz. Monzonite differ from the syenites fact that the Plagioklasfeldspäte outweigh the Kalifeldspäten in mineral content.

Mineral constituents

Syenite is chemically identical to the volcanic trachyte and ensure its in the earth's crust solidified equivalent dar. In the classification diagram of Streckeisen is syenite in box 7

Main mineral in alkali feldspar syenite is ( orthoclase or microcline ), lower the proportion of sodium- rich to intermediate plagioclase. Outweighs the alkali feldspar significantly (90 percent by volume ) over the plagioclase, it is a Alkalifeldspatsyenit. If quartz (up to 20 % ) is added, it is called Quarzsyenit or quartz Alkalifeldspatsyenit; at a Foidgehalt of up to 10 % of a leading - foid syenite or foid - leading Alkalifeldspatsyenit. Mafic minerals such as biotite, hornblende, clinopyroxene or olivine usually occur only in small quantities.

Rock description and name

Syenite is a medium-to coarse-grained igneous plutonic rock. Due to the mineral inventory of the syenite usually has a light gray or reddish color, but can sometimes also be very dark. The directionless - grained structure is very similar to that of granite. Although mostly medium - to coarse -grained, fine-grained syenite may also form aplitische or giant -grained pegmatitic transitions.

As it was previously difficult to determine exactly syenites, are available for groups of syenites variety names such as Larvikite ( with anorthoclase ), Nordmarkite ( with microcline ), Pulaskite ( with nepheline ) and Lusitanite ( with microcline ).

Occurrence and use

Syenite is distributed worldwide. It usually occurs in conjunction with other plutonic rocks on (granite, granodiorite ) is subject to, in terms of quantity but clear. In Germany he found, inter alia, in the Odenwald, the Black Forest and the Thuringian Forest. Other known deposits are found in, among others, in Norway at Larvik.

Syenite is hard and polish compatible and serves as a building block in addition to using as a starting material for sculpture works such as columns, slabs, plinths and the like. Many works of art from antiquity are made of syenite, which are especially found in Egypt ( at Sinai ) ( even if it is at the stone from the city of Syene the mineral content after more of a granite as a syenite is ).

Types of natural stone

• Cardinal Red ( South Africa)
• Balma ( Balma in Verbania, Piedmont in Italy)
• Larvikite, Also called black Labrador Emerald Pearl, ( Larvik, Norway)
• Blue Pearl, also called Labrador bright, ( Larvik, Norway)