How igneous rocks are formed
Igneous rocks are formed when either lava or magma are cooled. Producing a solid igneous rock
families of igneous rock
The felsic rock family forms from magma that contains a large proportion of silica.. This family of rocks are often characterized by their light color. An example of this rock is granite.
Rocks in the mafic family form from magma that contains low proportions of silica. this type of rock is characterized by their darker color. This family includes the rock of basalt.
Rocks in this family are made up of of the minerals feldspar, hornblende, pyroxene, and biotite mica. The rocks in this family consist of a middle-ground for the portions of silica they contain (not as high as felsic, not as low as mafic). An example of a rock in this family is diorite..
Igneous Rock textures
Fine-Grained texture means that mineral grains are present but too small to be seen with the naked eye. This indicates that the lava or magma cooled rapidly and did not allow the crystals to develop.
Course-Grained texture indicates that the mineral grains are quite large (large enough to be seen by the naked eye). This indicates that the lava or magma cooled slowly, allowing the crystals time to develop.. An example of this is gabbro.
intrusive and extrusive rocks
Intrusive rocks are igneous rocks that are formed with magma under the earth. Intrusive rocks are often characterized by their large crystal size. Some examples of intrusive rocks are granite, gabbro, and Andesite.
Extrusive rocks are igneous rocks that were formed above ground with lava. Extrusive rocks are often characterized by their small crystals. Some examples of extrusive rocks are obsidian, basalt, and scoria.