Igneous Rocks (#5 in Lab Text)
Name:_______________________________________
Briefly explain how igneous rocks form.
Molten rock beneath Earth's surface is called _________________.
Intrusive igneous rocks typically cool rapidly / slowly (circle best answer), resulting in large / small crystals (circle best answer).
Extrusive igneous rocks typically cool rapidly / slowly (circle best answer), resulting in large / small crystals (circle best answer).
Please briefly describe the following igneous rock textures:
Phaneritic:
Aphanitic:
Porphyritic:
Pycroclastic:
Glassy:
Vesicular:
In the context of igneous rocks, what does Color Index (Figure 5.3) mean?
Please list the 8 most common igneous rock-forming minerals:
Which of the above rock-forming minerals are "felsic"?
Which of the above rock-forming minerals are "mafic"?
An igneous rock that contains 0-15% mafic minerals is felsic / intermediate / mafic in composition (circle best answer).
An igneous rock that contains 16-45% mafic minerals is felsic / intermediate / mafic in composition (circle best answer).
An igneous rock that contains 46-85% mafic minerals is felsic / intermediate / mafic in composition (circle best answer).
Using the charts on page 92 and 93, complete the following sentences:
An igneous rock with a phaneritic texture and a color index of 10 contains abundant quartz, and more feldspar than mafic minerals. The feldspar is mostly K-spar. Based on the rock classification charts on p. 92 and 93, the name of this rock is ______________________.
An igneous rock with a glassy texture is __________________________.
A dark-colored igneous rock with an aphanitic texture and a color index of 55 is _____________________.
An igneous rock with a pyroclastic texture that contains fragments larger than 2 millimeters is __________________________________.
A mafic igneous rock with an aphanitic texture and abundant vesicles is _________________________.