What is Mica?
Mica is a group of minerals that are physically and chemically similar. These are sheet silicate minerals that have a nearly perfect basal cleavage and monoclinic crystal system. The mica group includes 37 phyllosilicate minerals. Mica splits into definite crystallographic structural planes. It is the most prominent characteristic of mica, which is explained by the hexagonal sheet-like arrangement of its atoms. Mica is a very important mineral that has been used in various fields of our life since prehistoric times. Mica was known to ancient Indian, Egyptian, Roman and Greek civilizations. We can find proof of its uses since ancient times as cave paintings, in pyramids, vessels, summer clothes, pottery, gulal and abir (coloured powder) etc. Mica mineral was used in the construction of Padmanabhapuram Palace which is a masterpiece of indigenous Kerala architecture. The third-largest pyramid of the world – The pyramid of the Sun, contains a good amount of mica in layers approximately up to 30cm thick. It is used in Ayurveda as well. Thus, we have been using mica in our everyday life for ages.
Uses of Mica Mineral
The world’s largest mica deposits are found in India in igneous, metamorphic, and sedimentary regions of Bihar and Nellore district of Madras. Mainly commercially important micas are muscovite and phlogopite. The unique properties of mica are very useful in various fields. The main applications of mica are listed below –
Uses of Mica in Everyday Life - Today, mica is used in almost everything - from the construction of buildings to makeup. 37 phyllosilicate minerals of the mica group possess platy texture and are used in fields. It is used as a pigment extender. Mica disc is used in breathing apparatus, communication devices, lenses, broadband waveplates etc. Mica is used in microwave ovens as well. Not only this, eyeliner or lip gloss that most women use on a daily basis also contains mica.
Uses of Mica Powder – We are using mica powder for various purposes especially for decorations for ages. Mica powder is used in clay pots, traditional Pueblo pottery, coloured powders, Kirazuri printing techniques or woodblock printmaking. It is also used in the decoration of windows of the buildings and to brighten the coloured pigments. It is widely used in cosmetics.
Uses of Mica Sheets – Mica sheets are mainly used as window sheets. Small pieces of mica sheets are used in toys as well. Sheet mica is used in electronics, microscopy, diaphragms for oxygen-breathing equipment, navigation compasses, thermal regulators, optical fibres, pyrometers (a type of thermometer used to measure the temperature of distant objects), stove or kerosene heater windows, mica thermic heaters etc.
As mica shows a refractive index that depends on the polarization and propagation direction of light, it is commonly used to make quarter and half-wave plates. The specialized use of mica is found in aircraft components and sea-launched missile systems. Apart from these, it is used in laser devices, radar systems and Geiger Muller tubes etc.
Uses of Mica in Cosmetics – Reflective and refractive properties of mica make it an important ingredient of cosmetic products. Mica is used in blushes, lipsticks, lip gloss, eyeliner, eye shadow, foundation, glitters, mascara, nail polish, moisturizing lotions etc. Some teeth whitening agents also contain mica. Mica creates a natural shimmery finish on the skin. It helps to give a more youthful and shinier, wrinkle-free look. Apart from these, mica does not react with skin and is suitable for all skin types.
Uses of Mica Paper – Mainly, mica paper is used in mica plates and mica tapes. Mica is an excellent electrical insulator while a good thermal conductor and high-temperature resistant (up to 1000℃). Due to these properties, mica tape is used in electrical and thermal appliances. It can also be used as a substitute for sheet mica. It is used for decorative purposes.
Uses of Mica in Medicines – We use mica in Ayurveda (ancient medicine prevalent in India). It is used in the preparation of various medicines for the treatment of respiratory and digestion-related diseases.
Other Uses of Mica – Thin and transparent sheets of mica are used in peepholes in lanterns, boilers, stoves etc. It is used to make capacitors for calibration standards. It is also used in transistors and high-pressure steam boilers.
Origin and Occurrence of Mica
Micas can form as a result of a variety of processes under a variety of situations. Crystallization from consolidating magmas, deposition by fluids derived from or directly associated with magmatic activities, deposition by fluids circulating during both contact and regional metamorphism, and formation as a result of alteration processes involving minerals such as feldspars are all examples of their occurrences, which are listed below. Micas' stability ranges have been studied in the lab, and their presence (rather than absence) or some part of their chemical composition may function as geothermometers or geobarometers in specific situations.
Mica crystals can be found in a few rocks, including certain igneous rocks and pegmatites. Micas that form huge crystals are known as books, and they can be several metres across. Micas are found in most rocks as irregular tabular masses of thin plates (flakes), which can look bent in some cases. Despite the fact that some mica grains are incredibly minute, all of them, with the exception of those found in sericitic bulk, have distinctive shiny cleavage surfaces.
Mica - List of Common Rocks
Micas that form common rock are found all throughout the world. The following are the more significant events:
Biotite is found in many igneous rocks (such as granites and granodiorites), as well as numerous pegmatite masses and metamorphic rocks (e.g., gneisses, schists, and hornfelsed). It is scarce in sediments and sedimentary rocks because it changes readily during chemical weathering. The weathering of biotite has caused some uncertainty at one point. Biotite loses its flexibility and turns into silvery grey flakes as a result of chemical weathering. Weathered biotite is golden yellow with a bronzy sheen in an intermediate stage that can be mistaken for gold flakes by novice observers.
Phlogopite is uncommon in igneous rocks, however, it can be found in ultramafic (silica-poor) rocks. It can be found in some peridotites, particularly those known as kimberlites, which are the rocks that contain diamonds. Some magnesium-rich pegmatites contain phlogopite, which is an uncommon component.
Muscovite is found in metamorphic gneisses, schists, and phyllites in particular. Muscovite occurs as minute grains (sericite) in fine-grained foliated rocks like phyllites, giving these rocks their silky luster. Muscovite is also found in various granitic rocks. It is abundant in complicated granitic pegmatites and miarolitic druses. Much of the muscovite in igneous rocks are assumed to have originated late in the parent magma's consolidation, or shortly afterwards. Muscovite is a weather-resistant mineral that can be found in various soils formed over muscovite-bearing rocks, as well as clastic deposits and sedimentary rocks produced from them.
Only a few gneisses, schists, and phyllites have been confirmed to contain paragonite, which appears to play a similar role to muscovite. It's possible, however, that it's a lot more prevalent than people think. It is because all light-coloured micas in rocks were mistakenly labelled as muscovites until recently without examining their potassium to sodium ratios, some paragonites may have been mistakenly identified as muscovites. It weathers in much the same way that muscovite does. Lepidolite is nearly primarily found in complicated lithium-bearing pegmatites, while it has also been found in a few granites.
As previously stated, glauconite is developing in several modern-day marine settings. It's also a prevalent component of sedimentary rocks, whose precursor sediments are thought to have been deposited on old continental shelves' deeper sections. Greensand is a term used to describe glauconite-rich sediments. The most common form of glauconite is granules, which are sometimes known as pellets. It's also available as a pigment, usually in the form of films that coat a variety of substrates like fossils, faeces pellets, and clastic debris.
Fun Facts About Mica
Mica minerals are aluminosilicates containing different metals. They disintegrated into fine sheets.
Mica is a group of materials with complete basal cleavage that are closely related.
They're all monoclinic, which means their crystals are all the same shape. They have a similar chemical composition and prefer to form pseudo-hexagonal crystals. The hexagonal sheet-like arrangement of mica's atoms explains its nearly perfect cleavage, which is its most notable feature.
Roger Wheeler with large book of mica found at Wheeler Mines 1961