Mineral Information and Data:

Phlogopite
KMg3(Si3Al)O10(OH)2 [CNMNC approved formula]

Named in 1841 from the Greek for firelike, referring to an oft-seen reddish tint. Redefined as the OH end-member by the IMA Mica Subcommittee in 1998.

IMA status : Approved Species 1998 ()
CLASSIFICATION 
Dana
(8th edition) :
71.02.02b.01  
  (71) Phyllosilicate Sheets of Six-Membered Rings
  (71.02) with 2:1 Layers
  (71.02.02b) Mica Group (Biotite subgroup)
  
Nickel-Strunz
(10th edition) :
09.EC.20
  (09) Silicates
  (09.E) Phyllosilicates
  (09.EC) Phyllosilicates with mica sheets, composed of tetrahedral and octahedral nets
  
Crystal system: Monoclinic System
Point group (H-M): 2/m — prismatic
Unit cell: a = 5.3 Å, b = 9.2 Å, c = 10.22 Å, β = 99.8°
Crystal Habit: Crystals prismated, tapered, plates, scales
Twinning: Common on {001} about [310] axis
  
Color: Yellowish brown to brownish red, colourless, white
Diaphaneity: Transparent to translucent
Luster: Pearly, sometimes slightly metallic on cleavage surfaces
Hardness (Mohs): 2 to 2.5
Measured Density: 2.76 to 2.90 g/cm3
Cleavage: 1; {001} perfect
Tenacity: Thin lamellae flexible and elastic, tough
Streak: White
  
Polymorphism and Series: Forms a series with biotite.
Polytypes: -1M, -3T and -2M1
Geologic Setting: In metamorphosed dolostones and magnesium-rich limestones; in ultramafic rocks as kimberlites, peridotites, lamproites, and serpentinites
Mineral Association: Dolomite, calcite, diopside, tremolite, scapolite, vesuvianite, apatite, titanite,
epidote, olivine, augite, magnetite
  
Synonyms/varieties: Flogopite, chromephlogopite (Cr-rich variety)

 

Phlogopite
Origin: Wilberforce, Canada
Sample size: 3 x 2 x 2.5 cm
Photo: Tom Loomis

 

Phlogopite
Phlogopite and hematite
Origin: Langban, Varmland, Sweden
Sample size: Microscopic image
Photo and Owner: Lou Perloff

 

Phlogopite
Origin: Faisabad, Kokcha Valley, Badakhshan, Afghanistan
Sample size: 4 x 4 x 3 cm
Photo: Tom Loomis

 

Phlogopite
(zoom-in of above)

<<< BACK TO MINERAL SEARCH