What does it mean if a rock has a fine texture?

Fine-grained textures generally indicate magmas that rapidly cooled at or near the Earth’s surface. Fast cooling prevents crystals from growing very large. The cutoff between fine- and coarse-grained textures is about 1 mm.

What is meant by a rock that has fine texture?

The fine-grained texture indicates the quickly cooling lava did not have time to grow large crystals. These tiny crystals can be viewed under a petrographic microscope [1]. In some cases, extrusive lava cools so rapidly it does not develop crystals at all.

What does it mean when a rock is fine grained?

i. Said of a crystalline rock, and of its texture, in which the individual minerals are relatively small; specif. said of an igneous rock whose particles have an average diameter less than 1 mm.

What causes some rocks to have fine grained texture?

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.

Are fine grained rocks smooth?

The magma, which is brought to the surface through fissures or volcanic eruptions, solidifies at a faster rate. Hence such rocks are smooth, crystalline and fine-grained.

How can you tell if a rock is fine grained?

Characteristics:

• Fine-grained – The grains are too fine to identify the minerals without a microscope.
• Some fine‑grained igneous rocks have rectangular crystals in them.
• Very hard! …
• Some volcanic rocks have vesicles, which are holes caused by gas bubbles when the lava was molten.

How is the texture describe if an igneous rock?

The texture of an igneous rock made up entirely of crystals big enough to be easily seen with the naked eye is phaneritic. Phaneritic texture is sometimes referred to as coarse-grained igneous texture. Granite, the most well known example of an intrusive igneous rock, has a phaneritic texture.

How do you describe the texture of a rock?

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 difference between an igneous rock with a glassy texture and a fine texture?

while igneous rock with a glassy texture is formed of rapid cooling of lava precisely due to quenching in water. while the igneous rock with a fine texture have an orderly arrangement of the atoms in the crystal and the crystals formed are too small that it cannot be seen by unaided eyes.

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.

Which igneous rocks are fine grained?

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.

How is fine grained igneous rock formed?

The magma, called lava when molten rock erupts on the surface, cools and solidifies almost instantly when it is exposed to the relatively cool temperature of the atmosphere. Quick cooling means that mineral crystals don’t have much time to grow, so these rocks have a very fine-grained or even glassy texture.

Where do igneous rocks with a fine-grained texture form?

Volcanic rocks are characteristically fine-grained. Volcanic rocks often exhibit structures caused by their eruption, e.g. flow banding (formed by shearing of the lava as it flows), and vesicles (open cavities that represent escaped gasses). Plutonic rocks form when magma cools within the Earth’s crust.

What is the difference between coarse grained and fine-grained texture?

Coarse-grained rocks generally weather faster than fine-grained rocks. In fine-grained rocks, the particles are fine and packed closely together. … Coarse-grained rocks have particles which are more loosely packed and is more susceptible to weathering.

What is required to generate an igneous rock with a fine-grained texture?

What is required to generate an igneous rock with a fine-grained texture? A fine-grained texture is the product of rapid cooling and crystallization of lava. … Mafic igneous rocks are rich in Fe, Mg, and Ca. You have found a mafic rock with a phaneritic texture.

What is the texture of an igneous rock referring to quizlet?

Igneous rocks are classified by texture (the size of mineral grains and/or distribution of grain sizes) and composition (the types of minerals present).

Why do igneous rocks have different textures?

The different sources of the melted material affects the textures of the igneous rocks. Also the amount of atmospheric gases and water that is mixed with the melted rock will affect the texture of the igneous rock. If the igneous rock is formed under the water this will have an effect on the texture.

What is rock texture quizlet?

Terms in this set (42) What is rock texture? the way a rock tastes. the way a rock feels.

How do you identify a rock in a picture?

Quote from video:If you can see crystals of minerals with well-defined regular shapes and these crystals are closely interlocking. Like a jigsaw. Then you have an igneous or metamorphic rock.

How can a rock change during metamorphism quizlet?

How does the mineral composition of rock change during metamorphism? hot magma inside the earth heats up the rocks and causes them to produce new minerals. The closer to the magma the rock is the more it changes. Or the rocks change when pressure builds up due to shifts in the Earth’s crust.

What does it mean when a metamorphic rock has foliation?

Foliated Metamorphic Rocks:



(Foliated means the parallel arrangement of certain mineral grains that gives the rock a striped appearance.) Foliation forms when pressure squeezes the flat or elongate minerals within a rock so they become aligned.

What does Nonfoliated mean?

‘Nonfoliated’ means ‘not banded‘ or ‘not layered. ‘ Some metamorphic rocks form so that they look as though they have layers, and these are said to be…

Why do differential stresses create foliation on rocks?

It is caused by shearing forces (pressures pushing different sections of the rock in different directions), or differential pressure (higher pressure from one direction than in others). The layers form parallel to the direction of the shear, or perpendicular to the direction of higher pressure.