题目：What is Marble and how is it formed? 内容：
What is Marble and how is it formed?
Marble is a rock composed of recrystallized carbonate minerals, with the maximum concentration of calcite or dolomite. Marble begins life as sedimentary rock known as limestone, which is a soft stone made primarily of calcite. Sedimentary rock is formed at or near the Earth’s surface by the accumulation and lithification of sediment (detrital rock).
Under heat and pressure caused by magma or the tectonic plates, this limestone begins to recrystallize, changing the texture of the rock and causing the calcite crystals to grow and interlock. Most marbles form at convergent plate boundaries. A large part of earth’s crust is exposed to metamorphism. During the process of metamorphism, the calcite recrystallizes that further changes the texture of beige marble. With the progression of the process, the crystals become larger and easily recognizable.
Marble is formed from limestone by heat and pressure in the earth’s crust. The conditions it is put under will cause the limestone to change in its very makeup, as well as texture and appearance, in a process known as crystallization. Large masses of calcite are created when the original carbonate and fossilized materials are recrystallized. And when there are impurities present in the limestone during this transformation, amazing effects and changes take place in the mineral composition. Depending upon the certain temperature, silica impurities react with the carbonate to produce crystals of quartz, or forsterite. At far higher temperatures and with rarer calcium minerals like larnite, other formations are created within the marble. There may also be a variety of other changes, depending on what’s present during the process, including water or other mineral components. Clay, sand, or chert mineral impurities may often produce distinctive veins and swirls within the marble, producing spectacular patterns and discolorations that homeowners and decorators are highly sought after.
Sedimentary rocks are the one that are formed on or near the surface of the Earth. Erosion, weathering, dissolution, precipitation, and lithification are the most important geological processes leading to the creation of sedimentary rocks. Sedimentary rocks were originally sediments, which were compacted under high pressure. Sedimentary rocks are formed through the solidification of sediments. They are formed when minerals and other sediment sit in oceans and lakes for millions of years. This sediment then further gets compressed over time and becomes solid layers of rocks. Further, earth movements can cause sedimentary rocks to be deeply buried or squeezed. As a result, the rocks are heated and put under great pressure. They do not melt, but the minerals they contain are changed chemically, forming metamorphic rocks.
Metamorphic rocks are rocks that have been changed from their original form by immense heat or pressure. The conditions necessary for the formation of a metamorphic rock are very precise and make it harder than sedimentary marble. The existing rock must be exposed to high heat, high pressure or a hot fluid rich in minerals. These conditions are most commonly found either deep in the crust of Earth or at the boundaries of plate where tectonic plates collide. In order to create metamorphic rock, it is vital that the existing rock remain solid and not melt. If there is too much heat or pressure, the rock will melt and become magma. This will result in the formation of an igneous rock, not a metamorphic rock.
What Are the Characteristics of Marble?
White marble is composed primarily of calcite, dolomite, or perhaps serpentine. The chemical composition of marble is composed of the following major constituents: Lime (CaO), Silica (SiO2), Alumina (Al2O3), oxides (NaO and MgO), and (MgCO3 and others). Marble has long been highly valued for its beauty, strength, and resistance to fire and erosion. It is known for its durability and its toughness to combat scratch and heat. The best thing about marble is that it is available in different colors due to the presence of various minerals like sand, silt and clay. Marble is usually a light-colored rock. When it is formed from a limestone with very few impurities, it will be white in color. Marble that contains impurities such as clay minerals, iron oxides, or bituminous material can be bluish, gray, pink, yellow, or black in color. Marbles of extremely high purity with a bright white color is very useful. Marble is a stone with a firm crystalline structure and slight porosity. Due to its structure, marble can be polished to improve its shine and is thus a common and attractive stone for building applications. These numerous virtues of marble make it one of the most coveted choices for the homeowners.
Marble has a diversity of physical properties that make it a useful stone. Below you will find some of the best reasons when marble is considered one of the most coveted choices:-
Value for money and resell value is high: Marble is a sturdy, solid and luxurious material that upgrades every space in which it is incorporated. It will present an elegant and distinguished look that will catch the eye of potential buyers. Marble comes with an everlasting appeal because it doesn’t get old easily. It is a stone which is very appreciated for its resistance and its ability to not lose its beauty over time. It increases the value of the property due to its characteristic combination which makes it a value for money material and it has higher resale value, higher valuation and it is reusable too.
