Gabbro Facts

Gabbro Facts
Gabbro is an igneous rock, is coarse-grained, dark-colored and intrusive. It is usually composed mainly of the minerals, calcium-rich plagioclase feldspar and augite. It may also contain small amounts of olivine and orthopyroxene, but very little amounts of quartz, unlike most igneous rocks. It is the most abundant rock in deep oceanic crust, and can be black or dark green in color. Gabbro is related to basalt because it is equivalent in its composition. However, basalt is extrusive, cools quickly, and has fine-grained crystals; whereas gabbro is intrusive, also cools slowly, but has coarse-grained crystals.
Interesting Gabbro Facts:
Gabbro color depends on its texture and on the environment where the rock is found. It is not a reliable property because it may change within the rock.
The top layer of the oceanic crust is basaltic, but the deeper rocks of the oceanic crust is made up of gabbro.
On continents, slow cooling allows large crystals to form as it is found within thick lava flows of basaltic composition.
Gabbro also appears when deep plutons form as magma chambers feed basaltic eruptions and crystallize.
Gabbro is found underground close to volcanoes, and in the oceanic crust near mid-ridge spreading centers.
Large amounts of gabbro can be found beneath extensive flood basalts of the Columbia River in Washington, Oregon, and the Deccan Traps of India.
Long belts of gabbro intrusions may be formed at proto-rift zones and around ancient rift zone margins.
The use of gabbro, especially when it is polished to a bright and shiny black luster is used to make cemetery markers, countertops for kitchens, floor tiling, facing stone, and other such stone products.
Gabbro stands up quite well to weathering, wear, and tear, which makes it a highly desirable rock because it requires the least amount of maintenance compared to other types of rocks used for the same products.
In the commercial stone industry black granite is the name used for gabbro. The black granite is used for products such as curbing, ashlars, paving stones, and other products.
A common use for gabbro is as a crushed stone or aggregate, and as a base material for construction products, road construction, railroad ballast, and anywhere else crushed stone is needed as a fill.
Gabbro may also contain very small amounts of some rare metals such as the mineral ilmenite, nickel, chromium, or platinum.
Occasionally gabbro rocks may contain cobalt, gold, or silver; but the amount depends on the individual minerals that formed each deposit.
The term gabbro was initially used in the 1760s. It referred to a set of rocks found in the ophiolites of the Apennine Mountains in Italy.
The term gabbro comes from a small village named Gabbro, located in a municipality of Tuscany.

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