Muscovite (also known as common mica, isinglass, or potash mica) is a phyllosilicate mineral of aluminium and potassium with formula KAl2(AlSi3O10)(F,OH)2, or (KF)2(Al2O3)3(SiO2)6(H2O). It has a highly perfect basal cleavage yielding remarkably thin laminae (sheets) which are often highly elastic. Sheets of muscovite 5 m × 3 m have been found in Nellore, India.
Muscovite has a Mohs hardness of 2–2.25 parallel to the [001] face, 4 perpendicular to the [001] and a specific gravity of 2.76–3. It can be colourless or tinted through grays, browns, greens, yellows, or (rarely) violet or red, and can be transparent or translucent. It is anisotropic and has high birefringence. Its crystal system is monoclinic. The green, chromium-rich variety is called fuchsite; mariposite is also a chromium-rich type of muscovite.
Muscovite is the most common mica, found in granites, pegmatites, gneisses, and schists, and as a contact metamorphic rock or as a secondary mineral resulting from the alteration of topaz, feldspar, kyanite, etc. In pegmatites, it is often found in immense sheets that are commercially valuable. Muscovite is in demand for the manufacture of fireproofing and insulating materials and to some extent as a lubricant.
The EarthCache
In the locality indicated by the coordinates look for the block of granite in the shape of the map of Angola. Here look for the minerals that shine the most in the sun (and in the light of the street lamps if you go at night). Here are the questions to validate your FOUND:
1- How large are the muscovite crystals on average?
2- Of the total volume of the block, what percentage do you consider to be muscovite?
If you feel you have all the answers correct, please log your found but also send me the answers via e-mail so I can check them. If I don’t answer you it is because they are correct and you have another found.Please note that when you e-mail me, please supply the reference (GC700T6) and name (Musvovite - DP/EC 81) of the cache and please click on the “I want to send my e-mail address along with this message” so that when I reply to you the messages don’t go into e-mail heaven (or hell).
Moscovite é um mineral do grupo dos filossilicatos (micas), com fórmula molecular : KAl2(Si3Al)O10(OH,F)2. A moscovite caracteriza-se pela clivagem de base bem marcada e distingue-se da biotite em amostra de mão por ser incolor. De acordo com as impurezas presentes, a moscovite pode ser incolor (mais comum), castanho claro, salmão, verde ou rosa. É um mineral muito comum nos granitos.
A moscovite é a mica mais comum encontrada em granitos, pegmatitos, gneisses e xistos, e como rocha metamórfica de contacto ou como mineral secundário resultante da alteração do topázio, feldspato, cianito, etc. Em pegmatitos, é freqüentemente encontrada em folhas imensas que são comercialmente valiosas. Moscovite é frequentemente utilizada para fazer materias resiotentes ao fogo e também para fabricar lubrificantes.
A EarthCache
Na localidade indicada pelas coordenadas procura o bloco de granito em forma do mapa de Angola. Aqui procura os minerais que mais brilham ao sol (e à luz dos candeeiros se fores à noite). Aqui responde às seguintes perguntas para validadares o teu FOUND:
- Que tamanho têm em media os cristais de muscovite?
- Do volume total do bloco, que percentagem estimas ser a muscovite?
Se achas que tens as respostas correctas, faz o teu log de "found", mas envia-me também as respostas por e-mail para que eu possa vê-las. Se eu não te responder é porque elas estão correctas.
Por favor, nota que quando me enviares um e-mail, por favor forneçe a referência (GC700T6) e nome (Muscovite - DP/EC81) da cache e clica em “I want to send my e-mail address along with this message”para que quando eu responder as mensagens não sigam para o saco roto do geocaching.com.
The most exciting way to learn about the Earth and its processes is to get into the outdoors and experience it first-hand. Visiting an Earthcache is a great outdoor activity the whole family can enjoy. An Earthcache is a special place that people can visit to learn about a unique geoscience feature or aspect of our Earth. Earthcaches include a set of educational notes and the details about where to find the location (latitude and longitude). Visitors to Earthcaches can see how our planet has been shaped by geological processes, how we manage the resources and how scientists gather evidence to learn about the Earth. To find out more click HERE.