The Leadhills Supergroup , formerly the Leadhills Group is a geological formation in Scotland. The Supergroup is named after the village of Leadhills .
19-857: Palaeoflow direction obtained from the horizons of the Corsewell Pont Conglomerate and the Glenn App Conglomerate indicates derivation from the north-west, presumed to be the Midland Valley arc. Dates of detrital muscovite and garnet are c. 480-460 Ma, indicating an origin from metamorphic activity during the exhumation of the Dalradian Supergroup after the Grampian Orogeny Greywackes , shales , siltstones and mudstones with conglomerates . Abereiddian Age to Ashgill Epoch The south-eastern boundary
38-553: A cheaper alternative to glass in windows. This usage became widely known in England during the sixteenth century with its first mention appearing in letters by George Turberville , the secretary of England's ambassador to the Russian tsar Ivan the Terrible , in 1568. Micas are distinguished from other minerals by their pseudohexagonal crystal shape and their perfect cleavage, which allows
57-499: A highly perfect basal cleavage yielding remarkably thin laminae (sheets) which are often highly elastic . Sheets of muscovite 5 meters × 3 meters (16.5 feet × 10 feet) 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 colorless or tinted through grays, violet or red, and can be transparent or translucent. It
76-561: A wide variety of electronics and as a filler in paints, plastic, and wallboard . It lends a silky luster to wallpaper . It is also used in tire manufacture as a mold release agent , in drilling mud , and in various cosmetics for its luster. George Turberville George Turberville , or Turbervile (about 1540 – before 1597) was an English poet. He was the second son of Henry Turberville of Winterborne Whitechurch , Dorset , and nephew of James Turberville , Bishop of Exeter. The Turbervilles were an old Dorsetshire family,
95-433: 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. It
114-515: Is characteristic of peraluminous rock , in which the content of aluminum is relatively high. 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 name muscovite comes from Muscovy-glass , a name given to the mineral in Elizabethan England due to its use in medieval Russia ( Muscovy ) as
133-410: Is composed of three sheets. The outer sheets ('T' or tetrahedral sheets) consist of silicon-oxygen tetrahedra and aluminium -oxygen tetrahedra, with three of the oxygen anions of each tetrahedron shared with neighboring tetrahedra to form a hexagonal sheet. The fourth oxygen anion in each tetrahedral sheet is called an apical oxygen anion. There are three silicon cations for each aluminium cation but
152-406: Is likely mistaken for muscovite often enough that it may be more common that is generally appreciated. Muscovite mica from Brazil is red due to manganese(3+). Like all mica minerals, muscovite is a phyllosilicate (sheet silicate) mineral with a TOT-c structure. In other words, a crystal of muscovite consists of layers ( TOT ) bonded to each other by potassium cations ( c ). Each layer
171-686: Is the Orlock Bridge Fault . This Scotland -related article is a stub . You can help Misplaced Pages by expanding it . This article about a specific stratigraphic formation in the United Kingdom is a stub . You can help Misplaced Pages by expanding it . Muscovite Muscovite (also known as common mica , isinglass , or potash mica ) is a hydrated phyllosilicate mineral of aluminium and potassium with formula KAl 2 (Al Si 3 O 10 )( F ,O H ) 2 , or ( KF ) 2 ( Al 2 O 3 ) 3 ( SiO 2 ) 6 ( H 2 O ). It has
190-559: The Heroycall Epistles of Ovid , and of the Eglogs of Mantuan (Gianbattista Spagnuoli, also known as Mantuanus ), and in 1568 A Plaine Path to Perfect Vertue from Dominicus Mancinus . The Book of Falconry or Hawking and the Noble Art of Venerie (printed together in 1575) are sometimes both assigned to Turberville though the second of these is a translation by George Gascoigne from
209-421: The 1 M polytype of the general mica structure. The formula for muscovite is typically given as KAl 2 (AlSi 3 O 10 )(OH) 2 , but it is common for small amounts of other elements to substitute for the main constituents. Alkali metals such as sodium , rubidium , and caesium substitute for potassium; magnesium , iron , lithium , chromium , titanium , or vanadium can substitute for aluminium in
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#1732852482349228-477: The French work La Venerie (1561) by Jacques du Fouilloux. The title page of his Tragical Tales (1587), which are translations from Boccaccio and Bandello , says that the book was written at the time of the author's unstated troubles. Wood says he was living and in high esteem in 1594. The booke of falconrie or hawking : for the onely delight and pleasure of all noblemen and gentlemen : collected out of
247-399: The arrangement of aluminium and silicon cations is largely disordered. The middle octahedral ( O ) sheet consists of aluminium cations that are each surrounded by six oxygen or hydroxide anions forming an octahedron, with the octahedrons sharing anions to form a hexagonal sheet similar to the tetrahedral sheets. The apical oxygen anions of the outer T sheets face inwards and are shared by
266-556: The court of Ivan the Terrible in 1568. Of his Poems describing the Places and Manners of the Country and People of Russia mentioned by Wood, only three metrical letters describing his adventures survive, and these were reprinted in Hakluyt's Voyages (1589). His Epitaphs, Epigrams, Songs and Sonnets appeared "newly corrected with additions" in 1567. In the same year he published translations of
285-400: The crystals to be pulled apart into very thin elastic sheets. Pyrophyllite , and talc are softer than micas and have a greasy feel, while chlorite is green in color and its cleavage sheets are inelastic. The other common mica mineral, biotite , is almost always much darker in color than muscovite. Paragonite can be difficult to distinguish from muscovite but is much less common, though it
304-414: The hydroxide. Muscovite in which the mole fraction of silicon is greater than aluminium, and magnesium or iron replaces some of the aluminium to maintain charge balance, is called phengite . Muscovite can be cleaved into very thin transparent sheets that can substitute for glass, particularly for high-temperature applications such as industrial furnace or oven windows. It is also used in the manufacture of
323-462: The inspiration for the d'Urbervilles of Thomas Hardy 's novel, Tess of the d'Urbervilles . Turberville became a scholar of Winchester College in 1554, and in 1561 was made a fellow of New College, Oxford . In 1562 he began to study law in London , and gained a reputation, according to Anthony à Wood , as a poet and man of affairs. He accompanied Thomas Randolph on a special mission to Moscow to
342-407: The octahedral sheet, binding the sheets firmly together. The relatively strong binding between oxygen anions and aluminium and silicon cations within a layer, compared with the weaker binding of potassium cations between layers, gives muscovite its perfect basal cleavage. In muscovite, alternate layers are slightly offset from each other, so that the structure repeats every two layers. This is called
361-438: The octahedral sheet; fluorine or chlorine can substitute for hydroxide; and the ratio of aluminium to silicon in the tetrahedral sheets can change to maintain charge balance where necessary (as when magnesium cations, with a charge of +2, substitute for aluminium ions, with a charge of +3). Up to 10% of the potassium may be replaced by sodium, and up to 20% of the hydroxide by fluorine. Chlorine rarely replaces more than 1% of
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