These fractures happen along with weak points in the mineral's structure. The weight of a mineral in the air is divided by the weight of an equal volume of water to determine its specific gravity (SG).Ĭleavage: Cleavage is the process of a gabbro breaking along smooth, flat planes. Specific gravity: The mass (weight) of a mineral divided by the mass (weight) of an equal amount of water is known as specific gravity. Streaks: The color of the powdered gabbro is known as a streak, and it is usually more useful for identification than the color of the full gabbro sample. When identifying a gabbro, color should be considered, but it should never be used as the primary identifier. Earthy, chalky, or dull are terms used to describe gabbro that lack luster.Ĭolor: Color is one of a mineral's most noticeable characteristics. The basic varieties of luster are described by the phrases metallic and nonmetallic. Luster: The luster of a mineral refers to how it reflects light. The capacity of one mineral to scratch another determines its hardness. Hardness: One of the most useful features for identifying gabbro is the capacity to resist being scratched, often known as hardness. Here are a few factors to consider while identifying gabbro: Gabbros are plutonic rocks that are chemically comparable to extrusive basalt and are generated by the cooling and crystallization of molten magma trapped beneath the earth's surface. Mafic minerals are sometimes known as ferromagnesian materials. Plagioclase feldspar with a high calcium content is common in mafic rocks. The most frequent rock-forming mafic minerals are olivine, pyroxene, amphibole, and biotite, which are all dark. A mafic mineral or rock is a magnesium and iron-rich silicate mineral or igneous rock. Mafic is a term used to characterize this type of rock. Gabbro is a phaneritic igneous rock that is high in iron, magnesium, and calcium but low in silica. Anorthosite is a gabbroic rock with less than 10% mafic mineral concentration. A rock that contains over 90% mafic minerals is classed as an ultramafic rock. Gabbros are classified as leucogabbro, which includes less than 35% mafic minerals, meso gabbros, which contain 35 to 65% mafic minerals, and melagabbros, which contain over 65 percent mafic minerals. Geologists have identified several subtypes of gabbro. Hornblende usually appears as a ring around augite crystals or as giant grains surrounding smaller grains of other minerals when it is present. Pyroxene and calcium-rich plagioclase make up gabbro, along with hornblende, olivine, and other minor minerals. He coined the term 'gabbro' to describe rocks that geologists today refer to as 'metagabbro'. The word was first employed more restrictively in 1809 by German geologist Christian Leopold von Buch in his description of these Italian ophiolitic rocks. ![]() Gabbro, a hamlet near Rosignano Marittimo in Tuscany, was the inspiration for the name. In the 1760s, the term 'gabbro' was coined to describe a group of rock types found in the Apennine Mountains' ophiolites. Today we will discuss one such intrusive igneous rock called ‘gabbro’. ![]() Some of the magma may fuel volcanoes on the surface, but the majority is confined beneath the surface, where it cools slowly over decades or millions of years before solidifying. Molten rock in large globs rises to the surface. ![]() When magma is imprisoned deep within the earth, intrusive, or plutonic, igneous rock occurs. ![]() Depending on where the molten rock hardens, igneous rocks are classified as intrusive or extrusive. The melt starts deep under the earth, around active plate borders or hot regions, and then rises to the surface. When a molten rock crystallizes and solidifies, igneous rocks form. In this post, we reveal everything you need to know about gabbro, including its meaning, colors, and uses.
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