What is Ophitic texture?

Ophitic texture is the association of lath-shaped euhedral crystals of plagioclase, grouped radially or in an irregular mesh, with surrounding or interstitial large anhedral crystals of pyroxene; it is characteristic of the common rock type known as diabase.

Which rock shows ophitic texture?

This texture is found in granites. Ophitic texture – laths of plagioclase in a coarse grained matrix of pyroxene crystals, wherein the plagioclase is totally surrounded by pyroxene grains. This texture is common in diabases and gabbros.

What causes ophitic texture?

The rate of heat loss (undercooling or supercooling) during the solidification is thus thought to cause ophitic texture, where pyroxene is growing rapidly and plagioclase is forming many more nuclei.

What does mineral texture mean?

Texture refers to the size, shape and arrangement of grains of one or more. minerals which make up the ore or rock. In rocks the features that determine. the texture are: crystallinity, granularity and fabric; however, ore minerals. are rarely, if ever, amorphous o crystallinity is not a variable in ores.

What texture is basalt?

Porphyritic Basalt

What is euhedral in geology?

Euhedral crystals (also known as idiomorphic or automorphic crystals) are those that are well-formed, with sharp, easily recognised faces.

What is Holocrystalline texture?

Said of the texture of an igneous rock composed entirely of crystals, i.e., having no glassy part. Also, said of a rock with such a texture.

Is quartz an aphanitic?

Aphanites are commonly porphyritic, having large crystals embedded in the fine groundmass, or matrix. The larger inclusions are called phenocrysts. They consist essentially of very small crystals of minerals such as plagioclase feldspar, with hornblende or augite, and may contain also biotite, quartz, and orthoclase.

What is poikilitic texture in geology?

Poikilitic texture describes the occurrence of one mineral that is irregularly scattered as diversely oriented crystals within much larger host crystals of another mineral.

What is the texture of pyroxene?

INTRODUCTION

What is directive texture?

Directive textures are produced by the preferred orientation of platy, tabular, or elongate mineral grains to yield grossly planar or linear arrangements; they are generally a result of magmatic flowage.

What is cumulate texture?

Cumulate rocks are igneous rocks formed by the accumulation of crystals from a magma either by settling or floating. Cumulate rocks are named according to their texture; cumulate texture is diagnostic of the conditions of formation of this group of igneous rocks.

What is Panidiomorphic texture?

Panidiomorphic refers to a texture in which, theoretically all the component mineral grains are subhedral. Allotriomorphic refers to a texture in which all the component mineral grains are anhedral.

What is directive texture in igneous rock?

Directive Textures: Those textures that indicate the result of flow of magma during the formation of rocks are known as directive textures. These exhibit perfect or semi-perfect parallelism of crystals or crystallites in the direction of the flow of magma. Trachytic and Trachytoid textures are common examples.

What is texture in igneous rocks?

Igneous textures include the rock textures occurring in igneous rocks. Igneous textures are used by geologists in determining the mode of origin of igneous rocks and are used in rock classification. There are six main types of textures; phaneritic, aphanitic, porphyritic, glassy, pyroclastic and pegmatitic.

What type of texture is igneous rocks?

There are nine main types of igneous rock textures: Phaneritic, vesicular, aphanitic, porphyritic, poikilitic, glassy, pyroclastic, equigranular, and spinifex. Each kind of texture has a variety of different characteristics that make them unique.

What is texture describe in brief the texture and structure of igneous rocks?

The texture of igneous rocks depends on the composition of the magma and the conditions surrounding the magma’s cooling. The textures are different in intrusive, vein, and extrusive rocks. Intrusive rocks are characterized by a holocrystalline texture, in which all the rock material is crystallized.

What do igneous rock textures say about the rock that formed?

The igneous texture tells us how the magma cooled and solidified. Magma can solidify into igneous rock in several different ways, each way resulting in a different igneous texture. Magma may stay within the earth, far below ground level, and crystallize into plutonic igneous rock (also known as intrusive igneous rock).

What is rock texture?

In rock: Texture. 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 texture of intrusive igneous rocks?

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. The individual crystals in phaneritic texture are readily visible to the unaided eye.

What are the three igneous rock textures?

Igneous Rock Textures

• COARSE GRAINED TEXTURE (PHANERITIC), mineral grains easily visible (grains several mm in size or larger)
• B) FINE GRAINED TEXTURE (APHANITIC), mineral grains smaller than 1mm (need hand lens or microscope to see minerals)
• C) PORPHYRITIC TEXTURE (MIXED FINE AND COARSE)

What textures are possible in intrusive rocks?

Intrusive igneous rocks will have either phaneritic, porphyritic, or pegmatitic textures.

What is an example of an igneous rock with coarse grained texture?

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.

What is coarse grained igneous 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.).

What is an example of a coarse grained felsic igneous rock?

For example, a coarse-grained, felsic igneous rock is not only a granite, it is an intrusive igneous rock that formed from slow cooling and crystallization of a body of magma within the earth’s crust. The intrusion of large bodies of granite—batholiths—is usually part of the origin of a mountain range.

How do you describe igneous rocks?

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).

What igneous means?

Definition of igneous

1a : formed by solidification of magma igneous rock. b : relating to, resulting from, or suggestive of the intrusion or extrusion of magma or volcanic activity. 2 : of, relating to, or resembling fire : fiery.

Are igneous rocks hard or soft?

hard

Igneous rocks are very hard and made of interlocking crystals.

What material is used to form igneous rocks?

Igneous Rocks: form by crystallizing melted material (magma). They can form either on the surface (extrusive igneous rocks), or deep in the crust (intrusive or plutonic igneous rocks). Volcanoes are places where magma erupts as lava or ash.