What are interlocking crystals?
Interlocking texture means that there is no space between individual crystals, because the crystals grew into one another. During cooling, crystals begin to form in the magma, much like ice crystals in a partially frozen drink. As cooling progresses and the crystals grow larger, only small pockets of liquid remain.
How are interlocking crystals formed?
Igneous rocks form by cooling and crystallization from a molten state. Therefore, they consist of interlocking crystals. Intrusive igneous rocks cool and crystallize slowly within the earth and so have coarse grains. Generally, the richer in silica and oxygen, the lighter colored the rock.
What is interlocking texture?
Due to how the three sorts of rock are formed, they appear quite different when you look at them closely. As igneous rocks begin to cool down from the molten state, the grains are crystals which grow together to form an interlocking texture, with the crystals touching each other. …
What does the texture of a rock tell you?
The texture of a rock is the size, shape, and arrangement of the grains (for sedimentary rocks) or crystals (for igneous and metamorphic rocks). Also of importance are the rock’s extent of homogeneity (i.e., uniformity of composition throughout) and the degree of isotropy.
What is the texture of plutonic rocks?
Plutonic rocks form when magma cools within the Earth’s crust. The rate of cooling of the magma is slow, allowing large crystals to grow. Plutonic rocks are characteristically coarse-grained.
What can crystal texture Tell us about rocks?
Geologists like igneous textures because they reveal so much about how a rock formed. Crystal size primarily reflects the rate of cooling, but is also often strongly affected by rock composition (especially water or gas content). Both intrusive and extrusive rock textures are represented.
What is the most common plutonic rock?
The most common rock types in plutons are granite, granodiorite, tonalite, monzonite, and quartz diorite. Generally light colored, coarse-grained plutons of these compositions are referred to as granitoids.
Why plutonic rocks have big crystals?
When magma cools underground, it cools very slowly and when lava cools above ground, it cools quickly. When magma and lava cool, mineral crystals start to form in the molten rock. Plutonic rocks, which cool slowly underground, have large crystals because the crystals had enough time to grow to a large size.
Why are mafic rocks dark colored?
Mafic rock, in geology, igneous rock that is dominated by the silicates pyroxene, amphibole, olivine, and mica. These minerals are high in magnesium and ferric oxides, and their presence gives mafic rock its characteristic dark colour.
What are dark-colored igneous rocks called?
Mafic Minerals
What 3 characteristics are used to classify igneous rocks?
Igneous rocks may be simply classified according to their chemical/mineral composition as felsic, intermediate, mafic, and ultramafic, and by texture or grain size: intrusive rocks are course grained (all crystals are visible to the naked eye) while extrusive rocks may be fine-grained (microscopic crystals) or glass ( …
What is the type of rock called that has 45 to 85% dark rock in it?
In a widely accepted silica-content classification scheme, rocks with more than 65 percent silica are called felsic; those with between 55 and 65 percent silica are intermediate; those with between 45 and 55 percent silica are mafic; and those with less than 45 percent are ultramafic.