Silicates in Igneous Rock

olivine remelts later nearer to the center of the earth, it is more mafic than it was in the first place.

If the magma is too thick, cooling will be more predictable. In an eruption, however, magma will move up and out of the magma chamber or may just move toward the surface and cool more quickly. The rest of the rock will often have a fine structure to it with respect to its quartz crystals. Porphyritic rock is rock that has a matrix of fine crystals with larger crystals in it. Look for different crystal size to call a rock porphyritic.

Figure 27 shows you the different magma temperatures and how the different types of rock crystallize:

SILICATES IN IGNEOUS ROCK

Figure 27.

Magma has just a few elements in it –the eight recently mentioned plus tiny amounts of titanium and phosphorus. Because of the high oxygen and silicon content of magma, it is essentially defined by these two elements. The viscosity of the magma, the temperature of the environment, and the gas content of the magma also count toward the rock's appearance in the end.