Table of Contents
Is a light-colored and coarse grained rock?
If there are lots of light-colored minerals and the rock is coarse grained, it is granite.
What rocks are coarse grained?
Coarse grain varieties (with mineral grains large enough to see without a magnifying glass) are called phaneritic. Granite and gabbro are examples of phaneritic igneous rocks. Fine grained rocks, where the individual grains are too small to see, are called aphanitic. Basalt is an example.
What is a coarse grained texture?
Coarse-grained textures generally indicate magmas that slowly cooled deep underground. Slow cooling gives crystals enough time to grow to easily seen sizes (i.e., larger than 1 mm). Thus, you can often figure out the relative order in which the minerals crystallized from the magma.
What is coarse grain mineral?
(a) Said of a crystalline rock, and of its texture, in which the individual minerals are relatively large; specif. said of an igneous rock whose particles have an average diameter greater than 5 mm (0.2 in.).
Is glassy a texture?
If a rock looks like a block of (colored) glass, with no visible mineral crystals, it has a glassy texture. Superficially, a glassy texture suggests cooling that was so extremely fast that no crystals could form. However, composition is also vitally important.
How is coarse-grained texture?
If magma cools slowly, deep within the crust, the resulting rock is called intrusive or plutonic. The slow cooling process allows crystals to grow large, giving the intrusive igneous rock a coarse-grained or phaneritic texture.
What is a foliated texture?
Foliation is described as the existence or appearance of layers. Foliated textures result from a parallel arrangement of flat, platy minerals. This is usually a result of mineral recrystallization in the presence of a directed pressure. Very flat foliation that resembles mineral cleavage.
How is coarse grained texture?
Which of these rock types has a fine grained texture?
Extrusive igneous rocks have a fine-grained or aphanitic texture, in which the grains are too small to see with the unaided eye. The fine-grained texture indicates the quickly cooling lava did not have time to grow large crystals.
Why does Obsidian have a fine grained texture?
Extrusive or volcanic rocks crystallize from lava at the earth’s surface. The texture of an igneous rock (fine-grained vs coarse-grained) is dependent on the rate of cooling of the melt: slow cooling allows large crystals to form, fast cooling yields small crystals. Volcanic glass is called obsidian.