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basalt fine porphyritic

Types of Porphyritic Rocks

Porphyry. — This name refers to the structure, which is formed of larger crystals set in a fine-grained or glassy ground-mass. The porphyritic structure may be plainly visible, the larger crystals being easily seen (phenocrysts), or it may require the microscope to bring it out. Porphyritic structure may appear in any igneous rock, but the true porphyries are rocks in which there is a marked ...

How to classify a rock: basalt - YouTube

Apr 07, 2017· Icelandic basalt columns on the East of Iceland - Duration: 2:22. takk76 Recommended for you. 2:22. A close look at dinosaur bones and fossil identification - Duration: 14:29.

Porphyry (geology) - Wikipedia

This property is common amongst most dense, fine-grained textured rocks, such as basalt. Density. The density of basalt is quite high, which can be seen through the combination of the rocks porosity: 0.1 – 1%, and its bulk density: 2.8 – 3 Mg (megagram) per m 3, This is because, around 50 percent of basalt …

What is a porphyritic igneous rock? - Quora

Sep 18, 2016· Thanks for the A2A. Igneous rock is formed through the cooling and solidification of magma or lava and is one of the three main rock groups, the two others being sedimentary and metamorphic. The word igneous comes from the Latin term ignis, which ...

Basalt - Homestead

Basalt is a common extrusive volcanic rock. It is usually gray to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or gray.

Andesite Rock | Properties, Composition, Formation, Uses

It has a porphyritic structure. The term 'porphyric' refers to the incorporation of large crystals into a fine-grained rock. The specific gravity of this rock is 2,5 – 2,8. It usually occurs in shades of gray. However, it is lighter in color than basalt. It is said that thicker or dome-shaped structures are formed.

Igneous Rock Textures - Indiana University

A hand specimen of basalt with aphanitic (fine grained) texture. The dark color is due to abundant dark colored minerals (pyroxene, hornblende). C) PORPHYRITIC TEXTURE (MIXED FINE AND COARSE) A hand specimen of a volcanic rock with porphyritic texture. Larger crystals of plagioclase feldspar (white), are suspended in a groundmass/matrix of fine ...

Basalt & andesite - Refine Industrial Co.,LIMITED

Basalt is an extrusive igneous rock, sometimes porphyritic, and is often both fine-grained and dense. Basalt in the tops of subaerial lava flows and cinders will often be highly vesiculated, imparting a lightweight "frothy" texture to the rock. The term basalt is often casually applied to shallow intrusive rocks with a composition typical of ...

Fine-Grained Porphyritic Textures

This is a fine-grained basalt with olivine phenocrysts (pale green blobs). This is an andesite with amphibole (hornblende) phenocrysts. This is a porphyritic rhyolite. The photo below is a close up. The blocky gray and white crystals are feldspar (one K-spar, one plag), and the dark gray, almost ...

Porphyritic basalt - Dunbar | Virtual Microscope

This altered porphyritic basalt sample is from The Battery, a ruined gun emplacement built towards the end of the 1700s during the American War of Independence, at the entrance to Old Harbour at Dunbar. It became disused by the middle 1800s and was subsequently re-used as a hospital.

What is the Basalt

Basalt is a common extrusive igneous (volcanic) rock. The basalt can be processed into basalt floor tiles, black basalt tiles, natural basalt stones, basalt stone tiles. Skip to content +86 [email protected]

L162 - porphyritic basalt · Igneous Rocks · 1A Collections

Fine-grained groundmass grew rapidly ... It is colourless to pale green in thin-section, has moderate relief and two cleavages which intersect at 56°. Rock Name. porphyritic basalt ← L161 - amygdaloidal basalt. L172 - ultramafic cumulate → ...

Basalt Textures - Michigan Technological University

Porphyrite or porphyritic basalt is characterized by obvious crystals, usually of plagioclase, which is often white or tan in color. These crystals are typically interpreted as phases that formed before eruption, where magma was being stored (a "Magma Chamber). On Isle Royale, there are five main examples of porphyritic basalt flows: The Scoville Point (psp), Hill Point (php) Tobin Harbor ...


Porphyritic felsites and basalts are widely distributed. The porphyritic texture indicates two separate stages of solidification. The porphyritic texture is common in extrusions, e.g., lava. Basalt-porphyry is a porphyry with basaltic chemism.

Basalt Rock | Formation, Properties, Composition, Uses

Basalt is the most common rock on Earth's surface. Specimens are black in color and weather to dark green or brown. Basalt is rich in iron and magnesium and is mainly composed of olivine, pyroxene, and plagioclase. Most specimens are compact, fine-grained, and glassy. They can also be porphyritic, with phenocrysts of olivine, augite, or ...

Geologic units containing Basalt - USGS

Dark-gray, fine-grained, dense, porphyritic in part, basalt flows in central and south-central part of State; commonly interbedded with conglomerate, sandstone, and siltstone. Includes small areas of rhyolite north of Cle Elum in Kittitas County, and andesite north of Leavenworth in Chelan County.

Basalt - an overview | ScienceDirect Topics

Tholeiitic basalt often represents a fine, glassy groundmass consisting of fine-grained quartz and other main constituent minerals. Tholeiitic basalt has fine-porphyritic texture, which is characterized by pyroxene/plagioclase phenocrysts (Fig. 4.39) in fine glassy groundmass.

Basalt - Igneous rocks

Basalt is a major rock type that occurs in virtually every tectonic setting. Basalt is clearly the most common volcanic rock on Earth and basaltic rocks (including gabbro, diabase and their metamorphosed equivalents) are the most common rocks in the crust 2.Basalt is also common on the Moon and other rocky planets of the Solar System.

basalt | Definition, Properties, & Facts | Britannica

Some basalts are quite glassy (tachylytes), and many are very fine-grained and compact. It is more usual, however, for them to exhibit porphyritic structure, with larger crystals (phenocrysts) of olivine, augite, or feldspar in a finely crystalline matrix (groundmass). Olivine and augite are the most common porphyritic minerals in basalts; porphyritic plagioclase feldspars are also found.

Porphyritic - Wikipedia

Rocks are said to be porphyritic if their groundmass is fine-grained ar aphanitic and porphyraceous if their groundmass in visible to the naked eye. Hence, rhyolite and basalt as fine-grained volcanic rocks are porphyritic and granite, syenite, etc. as coarse-grained plutonic rocks are porphyraceous. Phenocrysts that make up porphyry should be ...

Porphyritic granite | Porphyritic granite has the same ...

Feb 15, 2013· Porphyritic granite has the same chemistry & mineralogy as ordinary granite, but differs in the size range of its crystals. Granites are coarsely crystalline igneous rocks, having a phaneritic texture. Porphyritic granites have a mix of large & small crystals, but all crystals are still fairly decent-sized. Large crystals in a porphyritic rock are called phenocrysts.

Basalt - Igneous rocks

It has a porphyritic structure. The term 'porphyric' refers to the incorporation of large crystals into a fine-grained rock. The specific gravity of this rock is 2,5 – 2,8. It usually occurs in shades of gray. However, it is lighter in color than basalt. It is said that thicker or dome-shaped structures are formed.

Ophitic Texture -

Ta would be coarsely porphyritc Tb would be very fine grained porphyritic and Tc would be Trap. Keweenaw rift rocks include a somewhat rare textural variety of basalt called ophite or ophitic basalt. Ophitic texture is defined inconsistently, but it is an important variety of basalt texture where pyroxene ...

Igneous Rock Flashcards | Quizlet

Porphyritic texture is a very common texture in igneous rocks in which larger crystals (phenocrysts) are embedded in a fine-grained groundmass. Porphyry is an igneous rock that contains larger crystals (phenocrysts) in a fine-grained groundmass. K-feldspar phenocrysts in this sample.

Phenocryst & Porphyritic Textures | Science Trends

Aug 15, 2017· A phenocryst is a large crystal that visually stands out compared to the rest of the minerals. Phenocrysts are found in porphyritic textures where large grains are visible in volcanic extrusive rocks. Imagine hiking in Colorado when you come upon a rock with crystals, phenocrysts to be exact, the size of your fist.These phenocrysts are part of a larger porphyritic texture that grows under …

Basalt ~ Learning Geology

Basalt has a fine-grained mineral texture due to the molten rock cooling too quickly for large mineral crystals to grow; it is often porphyritic, containing larger crystals (phenocrysts) formed prior to the extrusion that brought the magma to the surface, embedded in a finer-grained matrix. These phenocrysts usually are of olivine or a calcium ...

Igneous Rock Textures

Porphyritic Rocks (the two images below show a hand sample and a thin section of porphyritic aphanitic textured rocks) : Porphyritic texture is really a subtype, but usage of the term often confuses the beginner. Porphyritic rocks are composed of at least two minerals having a conspicuous (large) difference in grain size.

Performance characteristics of tunnel boring machine in ...

The rock types encountered during excavation are fine compacted basalt, porphyritic basalt, amygdaloidal basalt, pyroclastic rocks with layers of red boles and intertrappean beds consisting of various types of shales. Relations between rock mass properties, physico-mechanical properties, TBM specifications and the corresponding TBM performance ...

Basalt Porphyry "Flowerstone" | Fred Haynes

Jun 06, 2017· "I believe that most of the "flower" porphyritic rock of Vancouver Island is from the Triassic Karmutsen Fm. There are feldspar porphyries in the older (Devonian) Sicker Gp. rocks, but I've never seen any flower patterns in those. I would call this basalt porphyry because most of the rock is sufficiently fine-grained to be volcanic.


Basalt A basalt is a fine-grained basic igneous rock containing essential calcic plagioclase feldspar and pyroxene (usually Augite), with or without olivine. Basalts can also contain quartz, hornblende, biotite, hypersthene (an orthopyroxene) and feldspathoids. Basalts are often porphyritic …

ROCKS and how to identify them.ppt - Sahra

ANDESITE is the fine-grained equivalent of DIORITE. It tends to be a darker gray than rhyolite and is often porphyritic, with visible hornblende. hornblende phenocrysts (*) Basalt - extrusive BASALT occurs as thin to massive lava. flows, sometimes accumulating to thicknesses of thousands of feet and covering thousands of square miles. The