What is Quartzite?
Quartzite is a non-foliated metamorphic rock that occurs when quartz enriched sandstone or chert is changed by the high temperature, pressure, and chemical activity of the metamorphism. These cause the quartz grains to infuse together to shape a dense, hard, equigranular (consisting of minerals of approximately the same size) rock. Quartzite rock is usually made up of more than 90% quartz; some specimens even consist of 99% quartz.
The biggest and purest concentration of silica on the earth's surface, Quartzite implies not only a high concentration of quartz but also a high degree of induration (hardness). Quartzite rock may look similar to quartz-rich sandstone, but the former has a glossy sheen.
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The intertwining crystalline structure of the rock makes it solid, hard, and durable. Quartzite is so hard that breakage occurs across quartz grains rather than breaking along boundaries between them. This unique feature separates quartzite rock from quartz enriched sandstone. Quartzite is generally white to gray in colour, but some with iron contents may appear pink. Some other trace minerals incorporated in quartz during metamorphism can make quartzite appear yellow, green, brown, blue, or orange. Apparently, quartzite may look the same as marble, but a metal blade cannot scrape a quartzite, and it will not exhibit effervescence with contact with dilute hydrochloric acid.
Quartzite Meaning
Quartzite is an extremely compact, hard granular rock primarily made of quartz. The high concentration of quartz in quartzite gives it a hardness of about seven on the Mohs Hardness Scale. The most crucial test to identify the mineral contents is the Mohs Hardness Test. The test is to check the comparative resistance of minerals being scuffed with ten minerals known as Mohs Hardness Scale, chronologically talc, gypsum, calcite, fluorite, apatite, orthoclase, quartz, topaz, corundum, and diamond. Its conchoidal fracture permits it to be curved into large cutting tools such as ax heads and scrapers. Due to its course structure, it is unfavorable to produce sharp edges like knife blades and shell points. Quartzite means metamorphosed sandstone.
Two forms of metamorphism create quartzite; contact and Barrovian. When molten magma gushes out and comes in contact with sandstone, it gets scorched and fuses so forcefully that it loses its inherent structure. The minerals crystallize firmly to produce quartzite. The deeper and hotter the sandstone gets, it blends more strongly.
Seafloor spreading occurs due to tectonic activities, which give rise to huge mountains. The massive forceful tectonic collisions produce extreme compression forces that consequently push, crush and squeeze sandstones. During these extreme exterior forces, sandstone metamorphoses into quartz, feldspar, amphibole, and biotite. Major physical changes occur during metamorphosis as all or most sedimentary properties, texture, and structure of sandstone undergo change. The super grain sand-paper-like exterior of sandstone turns into a glossy sheen. During this crystallization, former binding minerals like iron oxide, silica, clay, and carbonate migrate. These are considered impurities in quartzite rock and the reason for black quartzite, green, brown, or blue quartzite. Veining pattern in quartzite is also formed due to this process. Since the transition of sandstone to quartzite is gradual, some geologists suggest an intermediate rock called quartz arenite.
Quartzite Uses
Since quartzite is extremely durable and chemical and heat resistant, it is used as quartzite countertops in the kitchen; as quartzite is a decorative stone with varying colors and vein patterns, it is used in wall tiles, roof tiles, and also in flooring and staircase. Unlike sandstone, quartzite has a varying level of porosity depending on the porosity of the parent rock. Pure quartzites are used as a source of silica for metallurgical purposes and to manufacture silica bricks. Quartzites are also mined to paving blocks, riprap, railroad ballast, rod metal (crushed stone), and roofing granules.
Difference Between Quartz and Quartzite
The word quartz is used to describe various materials, ranging from a mineral consisting of silica and oxygen atoms to engineered stone material used to craft kitchen countertops. The latter is also referred to as quartz due to its predominant constitution. The quartz kitchen countertops contain a lot of mineral quartz mixed with a polymer resin (less than 10% of the weight), hence called quartz.
Quartzite is a metamorphic rock, while quartz is an igneous rock that crystallizes from magma or precipitates from hydrothermal vents of mid-ocean ridges. Sandstone metamorphoses under extreme heat, pressure, and chemical reaction from quartz arenite and quartzite. Quartzite is a metamorphic rock mainly consisting of quartz (more than 90%). Other minerals are feldspar, mica, magnetite, zircon, and rutile.
FAQs on Quartzite
1. What are the characteristics of quartzite?
The unique characteristics of quartzite are its durability and hardness at seventh in Mohs Hardness Scale, meaning it is harder than glass and knife blades. It is resistant to acids like diluted hydrochloric acid, vinegar, or lemon juice, making it ideal to use as kitchen countertops. On the other hand, marble and dolomitic marble will react to acids. Dolomitic marble reacts slightly slower than normal marbles, but quartzite will not scratch in normal kitchen acids. Quartzite has a different level of porosity. Some, like the Taj Mahal or Sea Pearl, are dense, closely infused due to high metamorphosis. Macaubas and Calacatta Macaubas are more porous as they have been less exposed to high pressure and temperature. Quartzite is scratch-resistant but not scratch-proof.
2. What are the three types of rocks?
There are three types of rocks, namely, Igneous, Metamorphic and Sedimentary. Igneous rocks are formed from magma, a mixture of molten rock, gas, and other volatile substances. Deep inside the earth, the temperature rises, eventually reaching the mantle, a solid rock behaving like a viscous liquid. When magma cools, it forms rocks; the process is slow, giving rise to crystals. There are two types of igneous rock; extrusive and intrusive. Metamorphic rocks undergo severe metamorphosis, fundamentally changing the parent rock. There are two types of metamorphosis; contact/thermal and regional/dynamic. Sedimentary rocks are formed from sediments, a naturally occurring material that is weathered or eroded over time. Sedimentary rocks form due to deposition on water bodies or the earth's surface.
3. What are the uses of quartz?
Quartz and quartzite are minerals with multipurpose utility. Though these minerals are abundantly found in nature there, lie many differences between them. The key ingredient is silica or silicon dioxide (SiO2), a natural compound made of two abundant materials on earth; 59% of the earth's crust is made of silica. Quartz is considered purest in white form, but impurities in the atomic structure cause a spectrum of colors, including pink, brown, black, grey, yellow, and red. Some quartz has piezoelectric properties; they produce electricity under mechanical stress. For ages, they have been used in jewelry as semi-precious gemstones due to their crystalline, durable, polish-able nature. One of the primary uses of quartz is glassmaking; the silica dioxide with 99.9% purity is melted and cooled to give the desired shape and design.
