| 31. | Dark brown varieties of augite and rhombic pyroxene ( hypersthene or bronzite ) have been observed but are not common.
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| 32. | These rocks contain also iron oxides ( usually titaniferous ), apatite, sometimes sphene, augite, and olivine.
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| 33. | Pigeonite crystallizes in the monoclinic system, as does augite, and a miscibility gap exists between the two minerals.
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| 34. | Textural evidence of its breakdown to orthopyroxene plus augite may be present, as shown in the accompanying microscopic image.
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| 35. | The commonest ferromagnesian mineral is augite ( sometimes rich in sodium ), with olivine in the more basic varieties.
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| 36. | Most of the dolerites are fine to medium grained, dark grey rocks with augite and plagioclase as major constituents.
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| 37. | Augite, biotite, plagioclase and hornblende occur as microphenocrysts and comprise 1 % to 7 % of the andesite.
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| 38. | But the plutonic representatives of the same magma, granite and syenite contain biotite and hornblende far more commonly than augite.
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| 39. | In tholeiitic basalt, pyroxene ( augite and orthopyroxene or pigeonite ) and calcium-rich plagioclase are common phenocryst minerals.
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| 40. | Green augite and hypersthene form a considerable part of these rocks, they may contain also biotite, hornblende and quartz.
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