Igneous Rock Diorite
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Igneous Rock Diorite |
Igneous Rocks - DioriteColour: Speckled black and white in hand specimen; occasionally shades of dark green or pink. The dark minerals are more noticeable than in gabbro. Colour index: 40 to 90, but very variable, often over short distances.Grain size: Coarse; may be pegmatitic. Texture: Equigranular or porphyrithic. In porphyritic varieties the feldspar or hornblende may form phenocrysts. Diorites often vary rapidly in texture; an equigranular variety may grade into a porphyritic one within a few centimeters. They are sometimes foliated due to the roughly parallel arrangement of the minerals. Structure: Xenoliths are common. Mineralogy: Essentially plagioclase (oligoclase or andesine) and hornblende; biotite and/or pyroxene may occur. Alkali feldspar and quartz (quartz diorites) may be present, when diorite grades into granodiorite. Common accessory minerals are apatite, sphene and iron oxides. Field relations: Forms independent stocks, bosses and dykes, but also comprises local variants of masses of granite, and sometimes gabbro, into which they merge imperceptibly." (Hamilton et al 1976, 170) |
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Igneous Rocks:
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Rock types:
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