A graphic texture is an igneous rock texture in which an intergrowth of two minerals has the appearance of runic writing. ... Graphic textures are most commonly intergrowths of quartz and alkali feldspar in which the quartz appears as v-shaped inclusions enclosed by the feldspar.

How is graphic texture formed?

Graphic texture is commonly created by exsolution and devitrification and immiscibility processes in igneous rocks. It is called 'graphic' because the exsolved or devitrified minerals form lines and shapes which are reminiscent of writing.

What are the types of texture in geology?

There are six main types of textures; phaneritic, aphanitic, porphyritic, glassy, pyroclastic and pegmatitic. Aphanitic (a = not, phaner = visible) rocks in contrast to phaneritic rocks, typically form from lava which crystallize rapidly on or near Earth' surface.

What type of rock is graphic granite?

Graphic granite, found predominantly in granitic pegmatite, is a leucocratic granitic rock consisting of an intimate intergrowth of alkali feldspar and quartz with a distinctive texture as ancient cuneiform writing when viewed in certain cross sections.

Where is graphic granite found?

About Graphic graniteHide

This is found almost exclusively in granitic pegmatites, and is believed to result from simultaneous growth of the feldspar and quartz under conditions which favored the planar growth of feldspar and the rods of quartz.

Textures of Igneous Rocks Part-1 | Igneous petrology | Geology | Geography | GATE | NET | UPSC

20 related questions found

What is Ophitic texture in geology?

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.

How do you describe texture in geology?

Texture refers to the physical makeup of rock—namely, the size, shape, and arrangement (packing and orientation) of the discrete grains or particles of a sedimentary rock. Two main natural textural groupings exist for sedimentary rocks: clastic (or fragmental) and nonclastic (essentially crystalline).

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.

What are the 4 textures of igneous rocks?

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)

Where do you find peridotite?

Peridotite is the dominant rock of the upper part of Earth's mantle. The compositions of peridotite nodules found in certain basalts and diamond pipes (kimberlites) are of special interest, because they provide samples of Earth's mantle brought up from depths ranging from about 30 km to 200 km or more.

What is the texture of metamorphic rocks?

TEXTURES Textures of metamorphic rocks fall into two broad groups, FOLIATED and NON-FOLIATED. Foliation is produced in a rock by the parallel alignment of platy minerals (e.g., muscovite, biotite, chlorite), needle-like minerals (e.g., hornblende), or tabular minerals (e.g., feldspars).

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 in graphic designing?

Graphic design is a craft where professionals create visual content to communicate messages. By applying visual hierarchy and page layout techniques, designers use typography and pictures to meet users' specific needs and focus on the logic of displaying elements in interactive designs, to optimize the user experience.

What is Phaneritic and Aphanitic?

APHANITIC TEXTURE - Igneous rocks that form on the earth's surface have very fine-grained texture because the crystals are too small to see without magnification. PHANERITIC TEXTURE - Igneous rocks with large, visible crystals because the rock formed slowly in an underground magma chamber.

What is the meaning of Phaneritic?

[ făn′ə-rĭt′ĭk ] Of or relating to an igneous rock in which the crystals are so coarse that individual minerals can be distinguished with the naked eye. Phaneritic rocks are intrusive rocks that cooled slowly enough to allow significant crystal growth. Compare aphanitic.

Is obsidian a Phaneritic?

The result is a natural amorphous glass with few or no crystals. Examples include obsidian. ... The minerals in a phaneritic igneous rock are sufficiently large to see each individual crystal with the naked eye. Examples of phaneritic igneous rocks are gabbro, diorite and granite.

Why is obsidian black in color?

Pure obsidian is usually dark in appearance, though the color varies depending on the impurities present. Iron and other transition elements may give the obsidian a dark brown to black color. Most black obsidians contain nanoinclusions of magnetite, an iron oxide. Very few samples of obsidian are nearly colorless.

What type of rock is obsidian?

Rondi: Everyone, meet Obsidian , an igneous rock that from melted rock, or magma. Obsidian is an "extrusive” rock, which means it is made from magma that erupted out of a volcano. If it was an igneous rock that formed from magma underground and did not erupt, it would have been called an "intrusive" rock.

What is texture formation in art?

In the visual arts, texture is the perceived surface quality of a work of art. It is an element of two-dimensional and three-dimensional designs and is distinguished by its perceived visual and physical properties. Use of texture, along with other elements of design, can convey a variety of messages and emotions.

What is the difference between fabric and texture?

The difference is that texture is the feel or shape of a surface or substance; the smoothness, roughness, softness, etc of something while fabric is (originally|construction) structure, building.

How does a crystalline texture form?

Crystalline texture: Crystals are visible and form an interlocking network. Unlike igneous crystalline textures, however, sedimentary crystalline textures are typically formed from one mineral throughout the entire rock.

Is Ophitic texture found in peridotite?

Biotite and hornblende frequently enclose feldspar ophitically; less commonly iron oxides and sphene do so. In peridotites the "lustre-mottled" structure arises from pyroxene or hornblende enveloping olivine in the same manner.

What is Granophyric texture?

A granophyric texture is an intergrowth of quartz and alkali feldspar in an igneous rock that is less well defined than a graphic texture and often is somewhat radiating. Granophyric texture can be similar to micrographic texture and to the coarser graphic intergrowths of quartz and alkali feldspar common in pegmatite.

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.