Igneous Rock Diabase
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Igneous Rock Diabase |
Igneous Rocks - Diabase (Dolerite)Colour: When fresh it is black, dark-grey or green; may be mottled black and white.Grain size: Medium. Texture: Occasionally ophitic texture can be distinguished in hand specimen. May be porphyritic. Structure: Vesicles and amygdales occur. Sometimes has segregations of coarser rock enriched in feldspar. Mineralogy: Phenocrysts comprise olivine (olivine diabase) and/or pyroxene or plagioclase. The groundmass comprises the same minerals with iron oxide, and sometimes with some quartz, hornblende or biotite. Field relations: Dykes and sills. These may form swarms of hundreds or perhaps thousands of individual dykes or sills which often radiate from a single volcanic centre." (Hamilton et al 1976, 170) |
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Igneous Rocks:
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Rock types:
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