Also found in: Encyclopedia.


An igneous rock composed primarily of alkali feldspar together with other minerals, such as hornblende.

[Latin Syēnītēs (lapis), (stone) of Syene, from Syēnē, Syene, an ancient city of southern Egypt, from Greek Suēnē.]

sy′e·nit′ic (-nĭt′ĭk) adj.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Mentioned in ?
References in classic literature ?
[7] At the cataracts of the great rivers Orinoco, Nile, and Congo, the syenitic rocks are coated by a black substance, appearing as if they had been polished with plumbago.
The greenstones of the eastern domain are intruded by late-tectonic syenitic granitoids such as the Swan Lake Syenite, 800m east of Bombora.
point load tests on fourteen rock types including Sandstone Limestone Dolomite Marble and Syenitic Gneiss to determine possible correlation between UCS and PLI and established following linear relationship:
Several granitic, granodioritic, tonalitic, dioritic and syenitic intrusions close to the quartz veins and minor gold field soils were observed (Figures 12 and 13).
Summary: Thorium, the radioactive metal, present in natural sediments produced in the form of detritus minerals such as monazite, rutile, granitic complexes, syenitic complexes, thorite, thorianite and progenitor of U, Th and Ac series.
In contrast the A-type syenitic and metavolcanic rocks are probably related to the compositionally similar West Barneys River plutonic suite and younger volcanic rocks formed in an extensional regime.
Madagascar geology can be divided into two major domains: (1) the upper Proterozoic crystalline basement, characterized by high-grade metamorphic rocks of igneous and sedimentary origin, and by large gabbroic to granitic and syenitic plutons representing the roots of the axial zone of the East African orogenic belt; and (2) a Permian-Mesozoic to Tertiary sedimentary sequence, formed during more or less continuous subsidence of the Mahajanga, Morondava and Toliara basins, corresponding to the paleo-Mozambique channel.
Although it is relatively abundant, we consider that this fact explains its minor representativity in the coastal territories of the dividing Portuguese sector, where the sandy coasts and the sandstone cliffs (granitic and syenitic) alternate with limy coasts (Jurassic and Cretacean).
Paleoweathering profiles on syenitic and phonolitic bedrocks are widerspread not only in the present-day tropical and subtropical terrains (Brazil: Valeton et al., 1991; Schumann, 1993; Boulange and Colin, 1994; Cameroon: Bilong, 1988; Braun et al., 1990; Ivory Coast: Boulange et al., 1975), but also in some places within the Ohre/Eger Rift, NW Bohemia.
Other basaltic units and syenitic intrusions with ages 0.56 to 0.55 Ga are widely distributed (Puffer, 2002; Higgins and van Breemen, 1998).