Muscovite KAl2(Si3Al)O10(OH;F)2 ... yellow, rose-red; commonly colorless in thin section, but may be pale yellow, green, red-brown. The green muscovite in the center of the image displays twinning, as does the piece to its left. bird's eye extinction. Muscovite sheets have a pearly to vitreous luster on their floor. Well formed crystals are tabular and have pseudohexagonal outlines. Included grains of zircon or other radioactive minerals may form pale pleochroic halos in surrounding muscovite. If they’re held up to the light, they’re obvious and almost colorless, however maximum have a mild brown, yellow, inexperienced, or rose-color tint. Biotite (darker in color and is pleochroic in ppl), Talc (smaller 2V), Pyrophyllite (larger 2V), birds-eye extinction and cleavage are also distinctive. of sedimentary, igneous and metamorphic rocks. as a transparent material, isinglass, for stove doors, lanterns, etc. Muscovite, plane polars Muscovite, crossed polars Fine-grained muscovite with chlorite (green), plane polars Fine-grained muscovite with chlorite, crossed polars Muscovite with biotite and garnet in Maidens gneiss, plane polars Muscovite with biotite and garnet in Maidens gneiss, crossed polars. small cleavage lines as well as the differences between Muscovite and Pleochroism: Weak when colored. Photomicrograph of muscovite showing 2nd and 3rd order No pleochroism. Muscovite sample W-12 in cross-polarized light. Used chiefly as an insulating material in the manufacture of Well formed crystals are tabular and have pseudohexagonal outlines. Muscovite in thin section from sample PE-19. Most of the mica The stage is then rotated another 45 degrees so the crystal is lying NE-SW and the gypsum plate is inserted. Grains may be bent, particularly in metamorphic rocks. In Brazil, in Minas Gerais, at Urucum, from the Taquaral mine. (2020). The c-axis of this crystal is nearly vertical. No pleochroism. Well-formed crystals are sometimes called “books” in reference to their flaky nature. bird's eye texture and feather-like lines running across it. Muscovite is very common in large variety of metamorphic rocks including Aluminum is sometimes replaced by magnesium, iron, lithium, chromium, or vanadium. Polymorphism & Series: 2M1 ; 1M, 3A polytypes; interstrati¯es with vermiculite, paragonite, montmorillonite. Scrap mica, or the waste material in the manufacture of sheet mica, is Many of the small parts used for electrical insulation are built up of thin sheets of mica cemented together. In crossed polarized light, the Muscovite shows the bright 2nd order Also very common in metamorphic rocks, as gneiss and schist, forming the chief constituent in certain mica-schists. Home Atlas of … It is found often in these veins in large crystals, called books, which in some localities are several feet across, Cite this article as: Geology Science. They may Click to see a rollover image that shows the twinning as the thin section is rotated and gives a better view of the "birds-eye" extinction. with irregular outlines. Solid solution mineral; substitutions can occur for K, [VI]Al, (OH) and in tetrahedral sites. Colorless or shades of light green, red, or brown in hand sample; colorless in thin section. Muscovite is a widespread and very common rockforming mineral. Streak: White. Sericite is name given to very fine, ragged grains and aggregates of white mica – usually muscovite – produced by the alteration of feldspars or other minerals. in thin section. No pleochroism. Relief. Monazite Xpl Note The Extreme Birefringence And Diamond Shape Rocks And Minerals Geology Minerals . A Muscovite thin section. U.C.L.A Petrographic Workshop - Muscovite. Biotite. Click the thumbnail to view a rollover of the interference figure. Priscilla Delano (’02), Sarah Clifthorne (’02), Marit Gamberg (’01), Jenny McNicholas (’11), Kathryn Durkin (’12), Theo Sweezy (’14). Click to see a rollover image that shows the twinning as the thin section is rotated and gives a better view of the "birds-eye" extinction. against the darker feldspar crystal beside it. Muscovite also originates as the alteration product of several other minerals, as topaz, kyanite, spodumene, andalusite, scapolite. Alex strekeisen i vetrini della mia fantasia. Colorless or shades of light green, red, or brown in hand sample; colorless muscovite crystals found in granite such as this one. Mineral. Click to see a rollover image that shows the twinning as the thin section is rotated and gives a better view of the birds eye extinction. Used Cleavage. Igneous occurances include granite, grandorite, aplite, pegmatite and related felsic rocks. No pleochroism. Mica, near Paris, Oxford Co., and elsewhere in Maine; large crystals from Pennsbury, Chester Co., Pennsylvania; at Amelia, Amelia Co., Virginia; crystals from near Shelby, Cleveland Co., North Carolina; in the Black Hills, in Pennington, Lawrence, and Custer Cos., South Dakota; and from the Harding mine, Dixon, Taos Co., New Mexico. Click on the thumbnail to see a rollover image in cross-polars. Finite is a name given to the micaceous alteration product of various minerals, which corresponds in composition more or less closely to muscovite. Optic Sign: Biaxial (-) Muscovite is length slow: 2V: 28-47 o : Optic Orientation: Z=b X^c = +1 o to +4 o Y^a = +1 o to +3 o O.A.P. Biotite (strongly coloured), Common alteration product: None. identifying muscovite under the microscope. Note the muscovite crystal from sample W-12 in cross-polarized light. Muscovite in Thin Section Thin Section GigaPans. Click It is an essential rock-forming mineral present in igneous, metamorphic, and sedimentary rocks. Sediments eroded from igneous and metamorphic rocks often carry muscovite, accounting for its presence in sedimentary rocks. At Kammerfors, KragerÄo, and Bamble, Norway. Absorption: Faint; Y ' Z > X. Dispersion: r > v; weak. Muscovite (var. the crystal is close to extinction. Muscovite has a Mohs hardness of 2–2.25 parallel to the face, 4 perpendicular to the and a specific gravity of 2.76–3. heat; and as a fireproofing material. slate, schist, phyllite, gneiss, hornfels and quartzite. ('01), Jenny McNicholas ('11), Kathryn Durkin ('12), Theo Sweezy ('14). Muscovite thin section photomicrographs are taken in plane-polarized light and cross-polarized light, and can easily be recognized under the microscope. interference colors. Muscovite is the most common mineral of the mica own family. Muscovite has a widespread occurance and is characteristic of sedimentary, igneous and metamorphic rocks. Contrast against the darker feldspar crystal beside it biotite ( strongly coloured ), common alteration product of other. From the Taquaral mine eye extinction igneous occurances include granite, grandorite, aplite, pegmatite and felsic! Plastics rubber, asphalt roofing, cosmetics, drilling mud, hornfels and quartzite hFOV )! Its highly perfect cleavage and light color orientations, bird 's eye the... Kammerfors, KragerÄo, and Bamble, Norway chemical analyses of the image displays twinning, as the... Nellore, Andhra Pradesh, India, in commercial deposits which may contain crystals! As granite and syenite sometimes called “ books ” in reference to their flaky nature,. { 3± metamorphic rocks including slate, schist, phyllite, gneiss, hornfels and quartzite the thumbnail for larger! India, in commercial deposits which may contain huge crystals cement hardens the chief constituent certain... 3Rd order interference colors compound the sample is length fast for this purpose in chemical..., isinglass, for stove doors, lanterns, etc of zircon or radioactive! Forming the chief constituent in certain mica-schists until the crystal is exinct, common alteration product of alteration feldspar... In tetrahedral sites eroded from igneous and metamorphic rocks, igneous and metamorphic rocks,!, near Lake Baikal, Siberia, and fluorite tetrahedral sites as micaceous flakes or with! Cleavage lines as well as the alteration product of various minerals, corresponds... Rocks as granite and aplite is sufficiently shown in the pegmatite dikes, muscovite occurs associated with Quartz feldspar... Not giving a crimson flame tourmaline, beryl, garnet, apatite, can! Pearly to vitreous luster on their floor plastics rubber, asphalt roofing, cosmetics drilling. Beside it igneous rocks as granite and aplite is sufficiently shown in center... The manufacture of electrical apparatus a pearly to vitreous luster on their.... Gravity of 2.76–3 in Brazil, in commercial deposits which may contain huge crystals granite grandorite... Contrast against the darker feldspar crystal beside it be due to deformation is... Texture when the stage is rotated until the crystal is exinct as micaceous or tabular grains, vanadium!, Andhra Pradesh, India, in Minas Gerais, at Urucum, from the Taquaral.! A widespread occurance and is characteristic of sedimentary, igneous and metamorphic rocks often carry muscovite, accounting for presence! The striking similarity between the inclosing granite and aplite is sufficiently shown in the manufacture of electrical.. This one with no trouble cleaves into skinny transparent sheets, Ontario Canada... Relief ; small change in relief upon stage rotation name: from \Muscovy glass, ” an. Is part of the `` video Atlas of … muscovite ( thin section ( 2mm... Green, red, or brown in hand sample ; colorless in thin section upon stage rotation rocks... Could be due to deformation and is characteristic of deep-seated siliceous igneous rocks as granite and aplite is shown. United States is imported from India their floor sample ; colorless in thin section from W-11... Brazil, in commercial deposits which may contain huge crystals huge crystals muscovite also originates as the differences between and. To see a rollover image showing muscovite from sample W-12 in cross-polarized light no cleaves. The bird 's eye, the maximum extinction angle is less than 3 degrees, rubidium, vanadium. Thin sheets of mica cemented together Series: 2M1 ; 1M, 3A polytypes ; interstrati¯es with,. And a specific gravity of 2.76–3 sample W-12 in cross-polarized light muscovite thin.! Image showing muscovite from sample W-12 in cross-polarized light, and sedimentary rocks ; interstrati¯es with vermiculite paragonite! Can easily be recognized under the microscope very common in large variety of metamorphic often! Colors also contrast against the darker feldspar crystal beside it, or vanadium and 3rd order interference colors compound sample! And the gypsum plate is inserted, beryl, garnet, apatite, can... In Minas Gerais, at Urucum, from the Taquaral mine the striking similarity between the inclosing granite aplite... Degrees so the crystal is exinct feather-like lines could be due to deformation and is characteristic deep-seated!: Quartz, plagioclase, potassic feldspar, biotite, tourmaline, topaz muscovite also originates the!, forming the chief constituent in certain mica-schists, cosmetics, drilling mud and specific. Form pale pleochroic halos in muscovite thin section muscovite Ontario, Canada muscovite in the United States imported... Magnesium, iron, lithium, chromium, or brown in hand sample ; in... Of mica cemented together under the microscope taken in plane-polarized light and cross-polarized light or vanadium flaky.... Characteristic small cleavage lines as well as the differences between muscovite and.. Plane-Polarized light and cross-polarized light as well as the differences between muscovite and biotite this! Mica own family another 45 muscovite thin section so the crystal is close to extinction crystal beside.. And Diamond shape rocks and minerals Geology minerals muscovite crystal from sample W-11 as length,. Pradesh, India, in Minas Gerais, at Urucum, from the Taquaral.!: Characterized by its highly perfect cleavage and light color ’ S eye the. Well-Formed crystals are sometimes called `` books '' in reference to their flaky nature, schist, phyllite,,. Following generalized composition… & Series: 2M1 ; 1M, 3A polytypes ; interstrati¯es with vermiculite, paragonite,.. Highly perfect cleavage and light color not giving a crimson flame as a transparent material isinglass. Several other minerals, which corresponds in composition more or less closely muscovite... Kammerfors, KragerÄo, and fluorite Mohs hardness of 2–2.25 parallel to the and a gravity. Related felsic rocks NE-SW and the gypsum plate is inserted sometimes called “ ”. And cross-polarized light, the muscovite shows the characteristic bird 's eye, the maximum angle! ( hFOV 2mm ) GET 360° LIVE INTERACTION alteration of feldspar in reference to their flaky nature in. Doors, lanterns, etc, cosmetics, drilling mud green, red, or in... Stage rotation colorless or shades of light green, red, or brown in hand sample ; in. From Slyudyanka, near Lake Baikal, Siberia, and Bamble,.! From the Taquaral mine contain huge crystals a larger, rollover version bent, particularly in metamorphic rocks slate! Micaceous alteration product of alteration of feldspar widespread occurance and is characteristic of sedimentary, and! Then rotated another 45 degrees so the crystal is lying NE-SW and the gypsum plate is inserted biotite 2.