Phlogopite

Phlogopite is a belonging to the micas, often occurring mineral from the mineral class of " silicates and Germanates ". It crystallizes in the monoclinic crystal system with the composition KMg3 [( F, OH ) 2 | AlSi3O10 ], and is therefore chemically seen a potassium -magnesium aluminosilicate with additional fluoride or hydroxide ions. Structurally phlogopite is assigned to the layer silicates.

Phlogopite developed mostly tabular to prismatic crystals of pseudohexagonalem habit, but also platy, foliated or massive mineral aggregates of mostly yellowish to reddish color. However, the mineral can also occur in colorless or light brown or greenish color.

Special Features

, Diluted 5 to 15 % hydrochloric acid is insensitive phlogopite, concentrated hydrochloric acid, however, the mineral decolorized.

Etymology and history

Phlogopite in 1841 was first described scientifically by August Breithaupt, who examined a " with serpentine in calcite ingrown mica of Antwerp in New York State " and him as " Phengites Phlogopites " - short phlogopite - designated, after the Greek word Φλογωπός [ phlogopos ] for " fiery -looking ". The name refers to the often translucent, reddish crystals.

Classification

In the now outdated but still in use classification of minerals according to Strunz ( 8th edition ) of the phlogopite belonged to the department of " layer silicates ( phyllosilicates ) " and there to the mica group, subgroup " Lithionit biotite - series" with the system no. VIII/H.11.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the phlogopite also in the department of " layer silicates ( phyllosilicates ) " a. However, this is further subdivided according to the type of film formation, so that the mineral according to its construction in the subdivision of " layer silicates ( phyllosilicates ) with mica sheets, composed of tetrahedral and octahedral nets " can be found where it as a name, the " phlogopite group "with the system number. 9.EC.20 forms.

The mostly commonly used in English-speaking classification of minerals according to Dana assigns the phlogopite also in the Department of phyllosilicates. Here he is in the " mica group ( biotite - subgroup ) " with the system no. To find " layers of six-membered rings with 2:1 layers phyllosilicates " 71.02.02b within the subdivision of.

Education and Locations

Phlogopite is also at a pressure of 70 kbar still resistant, which corresponds to a depth of about 200 kilometers. It is formed in magnesium-rich, basic to ultrabasic igneous rocks such as melilithreichem " Turjait " ( biotite - nepheline Melilitolith with perovskite, Melanite and apatite ), but can also kontaktmetamorph and kontaktmetasomatisch arise in Kalksilikatgesteinen, that is penetrated by silicates limestones, the have undergone a metamorphosis. Also in ultramafic rocks such as kimberlite, peridotite, serpentinite phlogopite lamproite and can be found.

Accompanying minerals occur among others apatite, augite, calcite, diopside, dolomite, epidote, magnetite, olivine, pyrite, ruby, scapolite, spinel, sphene, tremolite and vesuvianite.

Worldwide phlogopite could be proven so far to over 1,250 localities (as of 2009). The largest crystals were, among others, in the Gardiner complex of Greenland ( 50 cm); at Kowdor / Murmansk ( 2 m) and Slyudiyanka / Irkutsk in Russia ( 5 m) and from the " Lacy Mine" in Ontario in Canada ( 10 x 5 m and up to 90 tonnes in weight ) to light. However, it should already have been with a diameter of 10 m and a weight of 270 t found phlogopite crystals.

Crystal structure

Phlogopite crystallizes in the monoclinic space group C2 / m ( Raumgruppen-Nr. 12) with the lattice parameters a = 5.33 Å; b = 9.22 Å; c = 10.22 Å and β = 100.03 °, and four formula units per unit cell.

Use

Phlogopite is used, inter alia in plastics, in substitutes for asbestos in cement joints in oil drilling sector, in pearl pigments and for the production of insulating materials in electrical engineering. Of industrial importance (eg for glass ceramics ) is the production of fluorine phlogopite.