Phlogopite
A phlogopite crumbled cleavage plate
General
Category	Mineral
Chemical formula	K(Mg,Fe,Mn)3Si3AlO10(F,OH)2)
Identification
Color	Yellowish- or greenish-brown
Crystal habit	Tabular, scaly masses, rarely perfect phenocryst tablets
Crystal system	Monoclinic
Cleavage	Perfect basal
Fracture	Bends without breaking
Mohs Scale hardness	2 to 2. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific A chemical formula is a way of expressing information about the Atoms that constitute a particular Chemical compound, and how the relationship between those atoms changes In Mineralogy, shape and size give rise to descriptive terms applied to the typical appearance or habit of Crystals The many terms used by mineralogists A crystal system is a category of Space groups which characterize Symmetry of structures in three dimensions with Translational symmetry in three directions In Crystallography, the monoclinic Crystal system is one of the 7 lattice Point groups A crystal system is described by three vectors. Cleavage, in Mineralogy, is the tendency of crystalline materials to split along definite planes creating smooth surfaces of which there are several named types In the field of Mineralogy, fracture is a term used to describe the shape and texture of the surface formed when a Mineral is broken The Mohs scale of mineral hardness characterizes the scratch resistance of various Minerals through the ability of a harder material to scratch a softer material 5
Luster	Pearly, sometimes slightly metallic
Refractive index	Transparent
Streak	Colorless

Phlogopite is a yellow, greenish or reddish brown member of the mica family of phyllosilicates. Lustre (or luster) is a description of the way light interacts with the surface of a Crystal, rock, or Mineral. The refractive index (or index of Refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves is reduced inside the medium The streak (also called powder color) of a Mineral is the Color of the powder produced when it is dragged across an unweathered surface The word "mica" is thought to be derived from the Latin word la micare, "glitteren" in reference to the brilliant appearance of this mineral (especially The silicate minerals make up the largest and most important class of rock-forming Minerals They are classified based on the structure of their silicate Ion group It is also known as magnesium mica. Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24

Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg₃AlSi₃O₁₀(F,OH)₂. Biotite is a common phyllosilicate Mineral within the Mica group with the approximate chemical formula K(Mg Fe3AlSi3O10(F A solid solution is a Solid - state Solution of one or more solutes in a Solvent. Potassium (pəˈtæsiəm is a Chemical element. It has the symbol K (kalium from qalīy Atomic number 19 and Atomic mass 39 Magnesium (mægˈniːziəm is a Chemical element with the symbol Mg, Atomic number 12 Atomic weight 24 WikipediaNaming Silicon (ˈsɪlɪkən or /ˈsɪlɪkɒn/ silicium is the Chemical element that has the symbol Si and Atomic number 14 Oxygen (from the Greek roots ὀξύς (oxys (acid literally "sharp" from the taste of acids and -γενής (-genēs (producer literally begetteris the Fluorine, fluorum meaning "to flow" is the Chemical element with the symbol F and Atomic number 9 Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1

For physical and optical identification, it shares most of the characteristic properties of the more common biotite, being distinguished from it by having a lighter colour with a hint of olive green. Biotite is a common phyllosilicate Mineral within the Mica group with the approximate chemical formula K(Mg Fe3AlSi3O10(F

Paragenesis

Phlogopite is an important and relatively common end-member composition of biotite. Phlogopite micas are found primarily in igneous rocks, although it is also common in contact metamorphic aureoles of intrusive igneous rocks with magnesian country rocks. Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change In Geology, an intrusion is a body of Igneous rock that has Crystallized from molten Magma below the surface of the Earth. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock

The occurrence of phlogopite mica within igneous rocks is difficult to constrain precisely because the primary control is rock composition as expected, but phlogopite is also controlled by conditions of crystallisation such as temperature, pressure and vapour content of the igneous rock. Crystallization is the (natural or artificial process of formation of solid Crystals precipitating from a homogeneous --> identical Solution Several igneous associations are noted; high-alumina basalts, ultrapotassic igneous rocks, and ultramafic rocks. Basalt (bəˈsɔːlt ˈbeisɔːlt ˈbæsɔːlt is a common Extrusive Volcanic rock. Ultrapotassic igneous rocks are a class of rare volumetrically minor generally Ultramafic or Mafic silica-depleted Igneous rocks. Ultramafic (also referred to as ultrabasic) rocks are igneous and meta -igneous rocks with very low Silica content (less than 45% generally

Basaltic association

The basaltic occurrence of phlogopite is in association with picrite basalts and high-alumina basalts. Picrite basalt is a variety of high-magnesium olivine Basalt that is very rich in the mineral Olivine. Phlogopite is stable in basaltic compositions at high pressures and is often present as partially resorbed phenocrysts or an accessory phase in basalts generated at depth. A phenocryst is a relatively large and usually conspicuous Crystal distinctly larger than the grains of the rock groundmass of a Porphyritic Igneous

Ultrapotassic association

Phlogopite mica is a commonly known phenocryst and groundmass phase within ultrapotassic igneous rocks such as lamprophyre, kimberlite, lamproite and other deeply-sourced ultramafic or high-magnesian melts. Lamprophyres ( Greek λαµπρός (lamprós = "bright" and φύρω (phýro = to mix are uncommon small volume ultrapotassic Igneous rocks Kimberlite is a type of potassic Volcanic rock best known for sometimes containing Diamonds It is named after the town of Kimberley in South Africa Lamproites are ultrapotassic mantle -derived volcanic rocks. They have low CaO Al2O3 Na2O high K2O/Al2O3 In this association phlogopite can form well preserved megacrystic plates to 10cm, and is present as the primary groundmass mineral, or in association with pargasite amphibole, olivine and pyroxene. Phlogopite in this association is a primary igneous mineral present because of the depth of melting and high vapour pressures.

Phlogopite bearing peridotite from Finero, Italy. Coin of 1 Swiss franc (diameter 23 mm) for scale. The franc ( German: Franken, French and Romansh: franc, Italian: franco; code: CHF The Millimetre ( American spelling: millimeter, symbol mm) is a unit of Length in the Metric system, equal to The phlogopites are the glittering minerals surrounded by the green groundmass of olivine. The matrix or groundmass of rock is the fine-grained mass of material in which larger grains or Crystals are embedded The Mineral olivine (when gem-quality also called Peridot) is a Magnesium Iron silicate with the formula ( Mg

Ultramafic rocks

Phlogopite is often found in association with ultramafic intrusions as a secondary alteration phase within metasomatic margins of large ultramafic to mafic layered intrusions. Metasomatism is the chemical alteration of a rock by Hydrothermal and other fluids Ultramafic to mafic layered intrusions are found in typically ancient Cratons and are rare but worldwide in distribution In some cases the phlogopite is considered to be produced by autogenic alteration during cooling. In other instances, metasomatism has resulted in phlogopite formation within large volumes, as in the ultramafic massif at Finero, Italy, within the Ivrea zone. Metasomatism is the chemical alteration of a rock by Hydrothermal and other fluids The Ivrea zone is a tectonic Terrane in the Italian Alps, that consists of a steeply dipping piece of the Earth ’s lower Trace phlogopite, again considered the result of metasomatism, is common within coarse-grained peridotite xenoliths carried up by kimberlite, and so phlogopite appears to be a common trace mineral in the uppermost part of the Earth's mantle. A peridotite is a dense coarse-grained Igneous rock, consisting mostly of the minerals Olivine and Pyroxene. This article concerns the geologic term for other uses see Xenolith (disambiguation A xenolith ( Greek: 'foreign rock' is a rock Kimberlite is a type of potassic Volcanic rock best known for sometimes containing Diamonds It is named after the town of Kimberley in South Africa The mantle is a part of an Astronomical object. The interior of the Earth, similar to the other Terrestrial planets, is Chemically divided Phlogopite is encountered as a primary igneous phenocryst within lamproites and lamprophyres, the result of highly fluid-rich melt compositions within the deep mantle. A phenocryst is a relatively large and usually conspicuous Crystal distinctly larger than the grains of the rock groundmass of a Porphyritic Igneous Lamproites are ultrapotassic mantle -derived volcanic rocks. They have low CaO Al2O3 Na2O high K2O/Al2O3 Lamprophyres ( Greek λαµπρός (lamprós = "bright" and φύρω (phýro = to mix are uncommon small volume ultrapotassic Igneous rocks

References

• Deer, W. A. , R. A. Howie, and J. Zussman (1963) Rock-forming minerals, v. 3, sheet silicates, p. 42-54
• Mineral Data Publishing, 2001 PDF
• MinDat entry
• Webmineral data