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Pseudo-hexagonal phlogopite crystal (size: 5.6 × 5.1 × 4.1 cm) from Franklin (Franklin Mining District), Sussex County, New Jersey, USA
General and classification
chemical formula KMg 3 [(F, OH) 2 | AlSi 3 O 10 ]
Mineral class
(and possibly department)
Layered silicates
System no. to Strunz
and to Dana
9.EC.20 ( 8th edition : VIII / H.11)
Similar minerals Biotite
Crystallographic Data
Crystal system monoclinic (pseudohexagonal)
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group C 2 / m (No. 12)Template: room group / 12
Lattice parameters a  = 5.33  Å ; b  = 9.22 Å; c  = 10.22 Å
β  = 100.03 °
Formula units Z  = 2
Frequent crystal faces {001}
Physical Properties
Mohs hardness 2 to 3
Density (g / cm 3 ) 2.78 to 2.85
Cleavage completely after {001}
Break ; Tenacity uneven
colour brown, gray, green, yellow, reddish brown
Line color White
transparency transparent to translucent
shine Glass gloss, pearlescent gloss
Crystal optics
Refractive indices n α  = 1.530 to 1.573
n β  = 1.557 to 1.617
n γ  = 1.558 to 1.618
Birefringence δ = 0.0280 to 0.0450
Optical character biaxial positive
Axis angle 2V = 16 to 20 °
Pleochroism colorless (pale yellow) to red-brown

Phlogopite is a frequently occurring mineral from the mineral class of " silicates and germanates " belonging to the mica . It crystallizes in the monoclinic crystal system with the composition KMg 3 [(F, OH) 2 | AlSi 3 O 10 ], so it is chemically a potassium - magnesium - aluminosilicate with additional fluorine or hydroxide ions . Structurally, phlogophite is assigned to layered silicates .

Phlogopite usually develops tabular to prismatic crystals with a pseudo-hexagonal habit , but also platy, scaly or massive mineral aggregates of mostly yellowish to reddish color. The mineral can, however, also appear colorless or light brown or greenish in color.

Etymology and history

Thin, translucent phlogopite with clear zone formation

Phlogopite was scientifically described for the first time in 1841 by August Breithaupt , who examined a "serpentine ingrown mica from Antwerp in New York State" and called it "Phengites Phlogopites" - phlogopite for short - after the Greek word Φλογωπός phlogopos for "looking fiery ". The name refers to the often translucent, reddish shimmering crystals.


In the meantime outdated, but still common classification of minerals by Strunz (8th edition) of phlogopite to the department of "belonged phyllosilicates (phyllosilicates)" and there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

The 9th edition of Strunz's mineral systematics , which has been in force since 2001 and is used by the International Mineralogical Association (IMA), also classifies phlogopite in the category of "phyllosilicates". This is, however, further subdivided according to the type of layer formation, so that the mineral, according to its structure, can be found in the subdivision of "layered silicates (phyllosilicates) with mica tablets, composed of tetrahedral and octahedral networks", where it is named after the "phlogopite group." “With the system no. 9.EC.20 forms.

The systematics of minerals according to Dana , which is mainly used in the English-speaking area , also classifies phlogopite in the layered silicate department. Here it is in the "mica group (biotite subgroup)" with the system no. 71.02.02b within the subsection of " Layered Silicates: Layers of six-membered rings with 2: 1 layers ".

Crystal structure

Phlogopite crystallizes monoclinically in the space group C 2 / m (space group no. 12) with the lattice parameters a  = 5.33  Å ; b  = 9.22 Å; c  = 10.22 Å and β = 100.03 ° as well as two formula units per unit cell . Template: room group / 12


Phlogopite is insensitive to dilute 5 to 15% hydrochloric acid , but concentrated hydrochloric acid discolors the mineral.

Education and Locations

Phlogopite (orange-red) with pyrite (shiny gold) in calcite

Phlogopite is still resistant even at a pressure of 70 kbar, which corresponds to a depth of over 200 kilometers. It is formed in magnesium-rich, basic to ultramafic igneous rocks such as melilithreichem "Turjait" ( biotite - nepheline -Melilitolith with perovskite , Melanit and apatite ), can also contact metamorphic and contact metasomatic arise in Kalksilikatgesteinen, that is traversed by silicates limestones that have undergone a metamorphosis. Phlogopite can also be found in ultramafic rocks such as kimberlite , peridotite , lamproit and serpentinite .

As Begleitminerale occur among other apatite , pyroxene , calcite , diopside , dolomite , epidote , magnetite , olivine , pyrite , ruby , scapolite , spinel , titanite , tremolite and Vesuvianit on.

So far, phlogopite has been detected at over 1250 sites worldwide (as of 2009). The largest crystals appeared in the Gardiner complex in Greenland (50 cm), near Kowdor / Murmansk (2 m) and Slyudjanka / Irkutsk in Russia (5 m) and from the "Lacy Mine" near Ontario in Canada (10 x 5 m and up to 90 t in weight). However, phlogopite crystals with a diameter of 10 m and a weight of 270 t are said to have been found.


Phlogopite is used, among other things, in plastics, in substitutes for asbestos, in joint cement, in the oil drilling sector, in mother-of-pearl pigments and for the production of insulating materials in electrical engineering . The production of fluorophlogopite is of technical importance (e.g. for glass ceramics).

See also


  • Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1979, ISBN 3-342-00288-3 , p. 586 .
  • Helmut Schrätze, Karl-Ludwig Weiner: Mineralogy. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp. 818 .
  • Paul Ramdohr , Hugo Strunz : Klockmann's textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, 1978, ISBN 3-432-82986-8 , pp. 747 .
  • Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 252 ( Dörfler Natur ).

Web links

Commons : Phlogopite  - collection of images, videos and audio files

Individual evidence

  1. ^ A b Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  666 .
  2. Webmineral - Phlogopite (English)
  3. a b c American Mineralogist Crystal Structure Database - Phlogopite (English, 2008)
  4. a b c Phlogopite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( [PDF; 79  kB ; accessed on June 22, 2017]).
  5. a b c d Mindat - Phlogopite (English)
  6. Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . 2nd Edition. Ott Verlag, Thun 1979, ISBN 3-7225-6265-1 , p. 291 .
  7. Mindat - Localities for phlogopite .