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Another specimen

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Typical Minerals
ORTHOCLASE - 65-100%
Plagioclase - 0-35%
Mafics - < 10%
Quartz - 0-5%
     A felsic igneous rock from the bottom of Bowen's Reaction Series. Typically light colored (few mafic minerals) with pink orthoclase being the most obvious mineral (although it can be white or greenish).
      Quartz is sometimes present but if it is between 5 and 20% the rock is a "quartz syenite." If quartz exceeds 20% the rock shifts into the alkali granite category.
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Tectonic Association
     Syenite, as with all felsic rocks, is found on continents. It is one of the last fractionation products and typically results from partial melting of the lower crust.
   Tectonic Cross Section - pdf version

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