Volcanic rocks are usually fine-grained or aphanitic to glass in texture.
The word texture has nothing to do with how the rock feels. Texture, in geology, is used to describe how the rock looks. The most noticeable textural feature of igneous rocks is grain size. Grain size refers to the size of the individual mineral crystals. Lava vs. Magma: Lava erupting from Kilauea in Hawaii (left); Sketch of magma deep in the earth (right): USGS Images. Intrusive vs. Extrusive Igneous rocks can be classified into two main categories: intrusive and extrusive. Igneous is used to describe rocks that crystallize out of hot molten material in the Earth called magma. When magma pushes up through Earth's crust to the surface, it is called lava. Both magma and lava cool and harden to form igneous rocks. Lava vs. Magma: Lava erupting from Kilauea in Hawaii (left); Sketch of magma deep in the earth (right): USGS Images. Intrusive vs. Extrusive Igneous rocks can be classified into two main categories: intrusive and extrusive. The sub-family of rocks that form from volcanic lava are called igneous volcanic rocks (to differentiate them from igneous rocks that form from magma below the surface, called igneous plutonic rocks). The lavas of different volcanoes, when cooled and hardened, differ much in their appearance and composition. Volcanic rocks are usually fine-grained or aphanitic to glass in texture. They often contain clasts of other rocks and phenocrysts. Phenocrysts are crystals that are larger than the matrix and are identifiable with the unaided eye. Extrusive igneous rocks come from lava. Lava, at the surface, is exposed to air and water which causes the molten rock to cool rapidly. Solidifying rocks at the surface cool too quickly for large crystals to form. Molecules in the lava do not have time to arrange themselves to form large crystals. Lava vs. Magma: Lava erupting from Kilauea in Hawaii (left); Sketch of magma deep in the earth (right): USGS Images. Intrusive vs. Extrusive Igneous rocks can be classified into two main categories: intrusive and extrusive. Types Of Lava Overview... When lava is underground in its molten state it is called magma. As it reaches the ground, and air, it is called lava. Once lava begins to harden it can turn into a variety of shapes and colors. The color of lava depends on the temperature of the flow as well as the chemical composition and any impurities that are in the liquid rock. An Igneous rock is the product of cooled solidified magma/lava. As magma/lava cools it goes through the process of crystallization which turns it into an igneous rock. The amount of time it takes for an igneous rock to form depends on its location and its composition. On the other hand an Intrusive igneous rock cools very slowly beneath the surface and is created by magma. Since the cooling process is very slow intrusive igneous rocks have very large crystals (coarse grained). In some instances there is also a third type of igneous rock. Technically it is an extrusive rock, but it resembles glass. This glass type of igneous rock forms when magma/lava is instantly cooled Extrusive igneous rocks come from lava. Lava, at the surface, is exposed to air and water which causes the molten rock to cool rapidly. Solidifying rocks at the surface cool too quickly for large crystals to form. Molecules in the lava do not have time to arrange themselves to form large crystals. Extrusive rocks have crystals that are too small to see without magnification. A common example of an extrusive igneous rock is basalt. Igneous textures include the rock textures occurring in igneous rocks. Igneous textures are used by geologists in determining the mode of origin igneous rocks and are used in rock classification. Pyroclastic (pyro = igneous, clastic = fragment) textures occur when explosive eruptions blast the lava into the air resulting in fragmental, typically glassy material which fall as volcanic ash, lapilli and volcanic bombs. Igneous is used to describe rocks that crystallize out of hot molten material in the Earth called magma. When magma pushes up through Earth's crust to the surface, it is called lava. Both magma and lava cool and harden to form igneous rocks. Solidifying rocks at the surface cool too quickly for large crystals to form. Molecules in the lava do not have time to arrange themselves to form large crystals. Extrusive rocks have crystals that are too small to see without magnification. A common example of an extrusive igneous rock is basalt.
http://web.calstatela.edu/faculty/ahamane2/psci183/psci183.activities/psci183.act2.rocks.hand.htm http://web.calstatela.edu/faculty/ahamane2/psci183/psci183.activities/psci183.act2.rocks.hand.htm https://en.wikipedia.org/wiki/Volcanic_rock http://web.calstatela.edu/faculty/ahamane2/psci183/psci183.activities/psci183.act2.rocks.hand.htm http://www.instanthawaii.com/cgi-bin/hi?Volcano.types http://www.arch.dcr.state.nc.us/ncarch/GeoArcheo/IgneousA.htm http://scienceviews.com/geology/igneous.html https://en.wikipedia.org/wiki/Igneous_textures http://scienceviews.com/geology/igneous.html
what texture does hardened lava give