Gabbro

The term "gabbro" was used in the 1760s to name a set of rock types that were found in the ophiolites of the Apennine Mountains in Italy. It was named after Gabbro, a hamlet near Rosignano Marittimo in Tuscany. Then, in 1809, the German geologist Christian Leopold von Buch used the term more restrictively in his description of these Italian ophiolitic rocks. He assigned the name "gabbro" to rocks that geologists nowadays would more strictly call "metagabbro" (metamorphosed gabbro)

Have you ever seen shiny black stone countertops or a black gravestone? Most people, including some manufacturers, will incorrectly label this black rock as being granite, when it is, in fact, gabbro. Gabbro actually has many uses, including building materials and as a source of metal, such as chromium and nickel. Have you ever seen shiny black stone countertops or a black gravestone? Most people, including some manufacturers, will incorrectly label this black rock as being granite, when it is, in fact, gabbro. Gabbro actually has many uses, including building materials and as a source of metal, such as chromium and nickel.

Gabbro can be formed as a massive, uniform intrusion via in-situ crystallisation of pyroxeneand plagioclase, or as part of a layered intrusionas a cumulate formed by settling of pyroxene and plagioclase. Cumulate gabbros are more properly termed pyroxene-plagioclase adcumulate.

Gabbro is an essential part of the oceanic crust, and can be found in many ophiolite complexes as parts of zones III and IV (sheeted dyke zoneto massive gabbro zone). Long belts of gabbroic intrusions are typically formed at proto-rift zones and around ancient rift zone margins, intruding into the rift flanks. Mantle plume hypotheses may rely on identifying mafic and ultramafic intrusions and coeval basalt volcanism.

Nearly all gabbros are found in plutonic bodies, but to restrict the term (as the International Union of Geological Sciences, IUGS, suggests) just to plutonic rocks is inappropriate, because gabbro may be found as a coarse- grained interior facies of certain thick lavas (see, for example). It is better to base a rock definition on descriptive characteristics of the rock rather than how or where it was formed.

Gabbro is an intrusive igneous rock that forms from the result of slow cooling of magma inside of a volcano. It is very similar to the fast cooling, extrusive basalt, as they both are formed from mafic magmas that contain dark colored minerals such as pyroxene, plagioclase, amphibole and olivine. We will go over what exactly this entire means in more detail now.

Gabbro Formation.

Gabbro forms in an intrusive setting, from the cooling and crystallization of magma underneath Earth's surface. Because it has a long time to cool, its crystals grow much larger than the crystals in its extrusive equivalent, basalt, do. Gabbro are commonly found underground approximately volcanoes, as well as in oceanic crust near mid-ocean ridge spreading centers. It contains a variety of dark colored minerals that are classified by geologists as being mafic. These minerals include pyroxene, plagioclase, amphibole, and olivine. They can also contain small amounts of iron-titanium oxides.

What Minerals are in Gabbro?

Gabbro is composed mainly of calcium-rich plagioclase feldspar (usually labradorite or bytownite) and clinopyroxene (augite). Minor amounts of olivine and orthopyroxene might also be present in the rock.

This mineral composition usually gives gabbro a black to very dark green color. A minor amount of light-colored mineral grains may also be present. Unlike many other igneous rocks, gabbro usually contains very little quartz. You can see a close-up view of gabbro toward the bottom of this page.

Gabbro in Oceanic Crust:

It is often stated that Earth's oceanic crust is made up of basalt. The word "basalt" is used because the rocks of the oceanic crust have a "basaltic" composition. However, only a thin surface veneer of oceanic crust is basalt. The deeper rocks of the oceanic crust are generally coarser-grained gabbro. Basalt occurs at the surface of the crust because the rocks there have cooled quickly. At greater depth the cooling rate is slower, and large crystals have time to develop. (See illustration.)

Gabbro in Continental Crust:

On the continents, gabbro can be found within thick lava flows of basaltic composition, where slow cooling allows large crystals to form. Gabbro will also be present in the deep plutons that form when magma chambers that feed basaltic eruptions crystallize.

Large volumes of gabbro are present beneath extensive flood basalts such as the Columbia River flood basalts of Washington and Oregon and the Deccan Traps of India.

Difference between gabbro and granite:

the distinction between granite and igneous rock is that granite is (rock) a bunch of igneous and intrusive rocks composed primarily of spar and quartz sometimes contains one or additional dark minerals, which can be translucent substance, pyroxene, or mineral granite is quarried for building stone, road gravel, ornamental stone, and tombstones common colours are grey, white, pink, and amber whereas igneous rock is (rock) a reputation originally given to a form of snaky, and currently typically used for a coarsely crystalline, rock consisting of lamellar mineral and labradorite.

The difference between granite and gabbro is that granite is (rock) a group of igneous and plutonic rocks composed primarily of feldspar and quartz usually contains one or more dark minerals, which may be mica, pyroxene, or amphibole granite is quarried for building stone, road gravel, decorative stone, and tombstones common colors are gray, white, pink, and yellow-brown while gabbro is (rock) a name originally given to a kind of serpentine, and now generally used for a coarsely crystalline, igneous rock consisting of lamellar pyroxene and labradorite. 

Uses of Gabbro:

Ocellar (orbicular) varieties of gabbro can be used as ornamental facing stones, paving stones and it is known by the trade name of 'black granite', which is a popular type of graveyard headstone used in funerary rites. It is also used in kitchens and their countertops under the misnomer of 'black granite'.

Gabbro typically contains valuable amounts of metal, nickel, cobalt, gold, silver, platinum, and copper sulfides.

Ocular (orbicular) sorts of igneous rock will be used as decorative facing stones, paving stones and it's additionally proverbial by the name of 'black granite', that may be a standard style of burying ground headstone utilized in ceremonial occasion rites. It is additionally utilized in kitchens and their countertops, additionally beneath the name of 'black granite.

Gabbro can be polished to a brilliant black luster. Brightly polished gabbro is used to make cemetery markers, kitchen counter tops, floor tiles, facing stone, and other dimension stone products. It is a highly desirable rock that stands up to weathering and wear. In the dimension stone industry, gabbro is sold under the name "black granite." Gabbro is also used to make a number of rough-cut products such as curbing, ashlars, paving stones, and other products. The most common use of gabbro is as a crushed stone or aggregate. Crushed gabbro is used as a base material in construction projects, as a crushed stone for road construction, as railroad ballast, and anywhere that a durable crushed stone is needed as fill.