| 41. | Cassiterite is a widespread minor constituent of igneous rocks.
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| 42. | He noted Andean-trending structures and discovered alkaline igneous rocks.
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| 43. | The main type of igneous rock is porphyritic diorite.
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| 44. | Silica-saturated igneous rocks fall in between these two classes.
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| 45. | These igneous rocks are some 390 million years old.
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| 46. | The extrusive igneous rock equivalent of granite is rhyolite.
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| 47. | Most major igneous rocks are found along this scale.
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| 48. | These minerals formed during the crystallization of igneous rocks.
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| 49. | Granite is an intrusive igneous rock, thus not volcanic.
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| 50. | Nephelinite is an example of a silica-undersaturated igneous rock.
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