What is a glassy igneous rock?

Description. A glassy igneous rock consists of dense volcanic glass. The very porous, foamy variety is called Pumice. The most important rock type belonging to this group is: obsidian.

What rock is glassy?

obsidian, igneous rock occurring as a natural glass formed by the rapid cooling of viscous lava from volcanoes. Obsidian is extremely rich in silica (about 65 to 80 percent), is low in water, and has a chemical composition similar to rhyolite. Obsidian has a glassy lustre and is slightly harder than window glass.

Why do igneous rocks have glassy texture?

Very quickly cooled lavas, typically those quenched in water, will have a glassy texture. They cool too quickly to form crystals. Glasses do not have an orderly arrangement of atoms and there are therefore no minerals, in the strict sense, in them. Volcanic glass is called obsidian.

What is igneous rock short answer?

Igneous rocks are defined as types of rocks that are formed when molten rock (rock liquefied by intense heat and pressure) cools to a solid state. Lava is molten rock flowing out of fissures or vents at volcanic centres (when cooled they form rocks such as basalt, rhyolite, or obsidian).

Where are glassy rocks formed?

Glassy or vitreous textures occur during some volcanic eruptions when the lava is quenched so rapidly that crystallization cannot occur. The result is a natural amorphous glass with few or no crystals. Examples include obsidian.

What is white volcanic glass called?

References. Obsidian (/ˌɒbˈsɪdiən/; /əb-/) is a naturally occurring volcanic glass formed when lava extruded from a volcano cools rapidly with minimal crystal growth.

What is coarse rock?

(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 glass a rock?

In nature, glasses are formed when sand and/or rocks, often high in silica, are heated to high temperatures and then cooled rapidly. The Glass in Nature display shows specimens of glass made in nature. Obsidian or volcanic glass, for example, is molten rock that has quickly cooled, becoming rock in a glassy state.

What igneous rocks have glassy texture?

Obsidian is the common rock that has a glassy texture, and is essentially volcanic glass. Obsidian is usually black.

What is the color of igneous rock?

Environment

What is igneous rock?

Igneous rock, any of various crystalline or glassy rocks formed by the cooling and solidification of molten earth material. They are hard, massive with no fossils and no pore spaces.

What is an example of extrusive igneous rock?

Examples of extrusive igneous rocks are basalt, pumice, tuff, etc. There are types of magma and these igneous rocks meaning comes from the type of magma they originate from. We will see the classification and properties of igneous rocks based on the magma.

Why do intrusive igneous rocks have coarse minerals?

In the intrusive igneous rock, the process of cooling is usually slow that allows the growth of large mineral crystals within the rocks. The feature of igneous rocks having coarse minerals is due to the crystals of the intrusive rocks. Examples of igneous rocks include granite, peridotite, diorite, and gabbro.

What are ultramafic igneous rocks?

Ultramafic Igneous Rocks: The characteristics of igneous rocks are mainly ferromagnesian and olivine in nature. For example, a slow cooking rock peridotite is a perfect example in this category. These igneous rocks cool down very slowly and are rare in nature.