MICA – FROM CAVES TO ELECTRICAL ENGINEERING

Mica has been with us since the beginning of our civilization. Its first confirmed use dates back to the Stone Age. Currently, mica is a group of 37 different silicate minerals, the most famous of which are phlogopite and muscovite. How did mica turn from a shiny painting powder into one of the most important materials in technology? Where do the names mica, muscovite and phlogopite come from? What connection does mica have with Tsar Peter I and cucumbers, and where can we find mica in our homes? 

The history of mica is incredibly long. Shiny-colored powder was used in cave paintings dating back to Paleolithic times. Later, the Egyptians made beads from it, and the Aztecs decorated their temples with mica, e.g. the Pyramid of the Sun in Teotihuacán. Mica was also widely used in the Roman Empire. The Romans decorated oil lamps with thin layers of mica, to change the color of the light. During the times of Tiberius, mica found another application. Pliny the Elder wrote that the second emperor of Rome had a great passion for... cucumbers. Augustus’ successor never went anywhere without his favorite delicacy, but Italian winters did not allow the imperial delicacy to be grown yearround. As a solution, the first specularium was built next to Tiberius’ house – a greenhouse with cucumber seedlings, which were taken out into the fresh air on warm days. It was the first documented greenhouse in human history. Its transparent windows were made of mica, which allowed a lot of light to pass through and insulated heat well, protecting the imperial specialities from frost. 

In the Middle Ages, the largest known reserves of mica were in Russia, where mica found another use. Delaminated thin pieces of mica were polished and inserted into the shutters of the princes’ and boyars’ houses. Mica worked much better than bull bladders or carp skin used in peasant huts at that time, because with a similar high transparency, it retained heat much better. With the development of industry and the discovery of huge deposits in the Urals, mica windows began to appear in peasant houses. Despite the dynamic development of glassmaking at the end of the 17th century, when the first glass began to appear in the homes of the Russian aristocracy, muscovite remained a strategic raw material of the duchy. 

During the reign of Tsar Peter I, mica became a key export raw material and was well known in Europe. Lumps of mica were transported from the port of Arkhangelsk to England and the Netherlands, from where they were transported by sea to countries and colonies around the world. In England during the Elizabethan era, mica imported from the Duchy of Moscow was called Moscow glass or muscovite (from the English Muscovy). 

Despite the well-developed glass industry in Europe, mica had many key advantages. The price of Moscow glass was times lower compared to ordinary glass that decorated the windows of churches and houses of the richest lords. Muscovite was also distinguished by a wide range of application temperatures – muscovite windows did not freeze in winter and withstood the temperature of flames in lanterns. Mica lumps also withstood impacts during transport better, which was extremely important for maritime trade at that time. 

In our days, almost everything related to mica has changed. Russia was rereplaced on world markets by India, China and African countries. The more important advantages of mica, apart from the price and frost resistance, are its dielectric and chemical resistance. 

The technology has also changed – now sheets of mica flakes are mostly used instead of whole lumps. After adding water and a binder to the flakes, a colloidal substance is formed, from which thin mica paper is produced. Several layers of such paper create mica sheets, which are an irreplaceable material in electrical engineering. Depending on the application, the sheets are produced from muscovite or phlogopite, less often from fluorophlogopite. Compared to muscovite, phlogopite has a darker golden color, which gives it its name from Greek phlogopos – resembling fire. Flogopit has a higher application temperature and slightly lower resistance to electrical breakdown. It is much softer, so it has a wide range of applications. Artificial mica or fluorophlogopite is also used in industry, but on a smaller scale due to its higher production price. 

Currently, mica is used in many industries. Paint manufacturers often add mica to increase gloss. Thanks to its chemical resistance, mica is also one of the components of ship hull coatings. We can find goods containing mica also in our homes. Mica plates can be found in our microwaves, and the cosmetics industry is the fourth largest user of this raw material. Thanks to its natural shine and non-toxicity, it has been widely used in makeup, shampoos, body mists, toothpastes and other products for a long time. Almost every shiny cosmetic product has this feature thanks to mica flakes. The word “mica” itself most likely comes from Latin Micare, meaning “to shine” or mica – “crumb”. 

Few raw materials have had such a wide range of uses as mica. Its unique combination of features means that we can be sure that the characteristic shine of mica will be with us for a long time.