Consistency refers to the fresh new physical attributes of your nutrients, including grains proportions. This describes new air conditioning reputation of the fresh new molten magma off which it cameposition refers to the rocks specific mineralogy and you will agents composition. Air conditioning history is additionally related to transform that will occur to the fresh new composition from igneous rocks.
If the magma cools slower, deep into the crust, the new ensuing rock is named invasive otherwise plutonic. Brand new slow cooling procedure lets crystals to enhance high, providing the intrusive igneous material a coarse-grained or phaneritic consistency. The individual crystals when you look at the phaneritic surface try easily noticeable to the brand new unaided vision.
Figure \(\PageIndex<1>\): Basalt is a classic fine-grained (aphanitic) extrusive igneous rock. This sample is mostly fine groundmass with a few small green phenocrysts that are the mineral olivine.
Whenever lava are extruded onto the surface, or intruded on the superficial fissures nearby the body and you may cools, the fresh new resulting igneous stone is named extrusive otherwise eruptive. Extrusive igneous rocks have an excellent-grained or aphanitic texture, where grain are way too short to see on unaided vision. The latest good-grained feel indicates new rapidly cooling lava didn’t have go out to enhance large deposits. These types of tiny crystals can be looked at around a great petrographic microscope .