Granodiorite
Image: <a href="//commons.wikimedia.org/wiki/User:Trougnouf" title="User:Trougnouf">trougnouf (Benoit Brummer)</a> (CC BY 4.0)
Mineral NameGranodiorite
Chemical FormulaComplex mixture of silicates (primarily SiO2, Al2O3, Na2O, K2O, CaO, FeO, MgO)
Mohs Hardness6
Streak ColorWhite to colorless
CleavageVariable; good in feldspar and mica, absent in quartz
FractureUneven to conchoidal
Specific Gravity2.65
Colorslight grey, whitish-grey, dark grey (specks)
TransparencyOpaque
Type LocalityStawamus Chief Provincial Park, Squamish, British Columbia, Canada
Mineral GroupIgneous Rock (Felsic intrusive)
Usesdimension stone, aggregate, construction material, monuments
Associated Mineralsquartz, plagioclase feldspar, orthoclase feldspar, biotite, hornblende
Raritycommon
Description
A large, light grey, somewhat rounded boulder with a rough, granular texture, resting on a flatter rock outcrop amidst a dense forest of evergreen trees.
Geological Context
Granodiorite is an intrusive igneous rock that forms from the slow crystallization of magma rich in silica and alkali metals deep beneath the Earth's surface. The Stawamus Chief is a prominent granodiorite pluton exposed by glacial erosion, forming a large dome.
