PHYLLOSILICATES CHEMICAL GROUP (http://www.minerals.net/minerals-Phyllosilicates-chemical_group.aspx)

Kaolinite Chemical Formula: Al2Si2O5(OH)4

Composition: Basic aluminum silicate

Crystal System: Triclinic

Environment: As a secondary altering mineral, usually from weathering,

in igneous, metamorphic, and sedimentary environments. Kaolinite is most often found

near the oxidized surface where it has altered from aluminum silicates such as feldspar

Rock Type: Igneous, Sedimentary, Metamorphic

POLYMORPHS: Dickite, Nacrite, Halloysite

COMMON MINERAL ASSOCIATIONS: Feldspar, Quartz, Calcite, Dolomite,

Barite

X-RAY DIFFRACTION [By Intensity (I/Io)]: 7.17(1), 1.49(0.9), 3.58(0.8)

Serpentine

Chemical Formula: The Serpentine group is composed of several related minerals. A

generic formula that includes all members is: X2-3Si2O5(OH)4, where X = Mg, Fe2+,

Fe3+, Ni , Al, Zn, or Mn (one of the two Si atoms may also be replaced by an Al or Fe

atom in a few rare members).

This leads to a complete formula of (Mg,Fe,Ni,Al,Zn,Mn)2-3(Si,Al,Fe)2O5(OH)4

The subscripted 2-3 after the first set of elements denotes that there are two or three of

the selected elements, depending on the charge of the element. Some very rare forms

of Serpentine contain water [H2O] in place of the hydroxyl [OH]. Since the charge of

water is different from hydroxyl, the formula of these rare forms is slightly altered.

The two most common members of the Serpentine Group are:

Antigorite - (Mg,Fe)3Si2O5(OH)4

Chrysotile - Mg3Si2O5(OH)4

Chrysotile is not a single mineral, but a group of polymorphous minerals with the

same chemical composition but different crystal lattice. Chrysotile polytypes are:

Clinochrysotile (monoclinic)

Orthochrysotile (orthorhombic)

Parachrysotile (orthorhombic)

Lizardite (hexagonal)

Other members of the Serpentine group are:

Amesite - Mg2Al(SiAl)O5(OH)4

Cronstedtite - Fe2+2Fe3+(SiFe3+)O5(OH)4

Fraipontite - (Zn,Al)3(Si,Al)2O5(OH)4

Nepouite - Ni3Si2O5(OH)4

Composition: Basic silicate of magnesium, iron, aluminum, nickel, zinc, and

manganese. (Some rare varieties contain water in place of the hydroxyl, and substitute

a different metal in exchange of the charge difference).

Crystal System: Monoclinic

Environment: Serpentine is fairly common in many environments, and is an important

rock forming mineral in many metamorphic environments.

Rock Type: Metamorphic

COMMON MINERAL ASSOCIATIONS: Talc, Magnesite, Dolomite, Brucite,

Olivine, Calcite, Magnetite. Amesite occurs with Diaspore.

Pyrophyllite

Chemical Formula: Al2Si4O10(OH)2

Composition: Basic aluminum silicate

Crystal System: Triclinic

Environment: In metamorphic schists and hydrothermal replacement deposits.

Rock Type: Metamorphic

COMMON MINERAL ASSOCIATIONS: Quartz, Chlorite, Hematite, Muscovite,

Albite, Rutile, Kyanite, Andalusite, Lazulite.

X-RAY DIFFRACTION [By Intensity (I/Io)]: 4.42(1), 9.2(0.9), 3.07(0.85)

Talc

Chemical Formula: Mg3Si4O10(OH)2

Composition: Basic magnesium silicate

Crystal System: Monoclinic

Environment: In metamorphic rocks, especially Serpentine deposits.

Rock Type: Metamorphic

COMMON MINERAL ASSOCIATIONS: Serpentine, Dolomite, Magnesite,

Actinolite, Olivine, Calcite, Magnetite, Brucite.

X-RAY DIFFRACTION [By Intensity (I/Io)]: 9.35(1), 1.53(0.55), 4.59(0.45)

Muscovite

Chemical Formula: KAl3Si3O10(OH)2

Variable Formula: K(Al,Cr,Mn)3Si3O10(OH)2

Composition: Basic potassium aluminum silicate, sometimes with some chromium or manganese

replacing the aluminum.

Crystal System: Monoclinic

Environment: Muscovite is a very common rock-forming mineral and is an important constituent in

many environments. Its presence is noted especially in granite pegmatites, in contact metamorphic rocks,

in metamorphic schists, and in hydrothermal veins. Important Muscovite deposits where large significant

crystals occur are almost exclusively from granite pegmatites.

Rock Type: Igneous, Metamorphic

COMMON MINERAL ASSOCIATIONS: Albite, Quartz, Microcline, Almandine,

Spodumene.

X-RAY DIFFRACTION [By Intensity (I/Io)]: 3.32(1), 9.95(0.95), 2.57(0.55)

Phlogopite

Chemical Formula: KMg3(AlSi3O10)(OH,F)2

Variable Formula: K(Mg,Fe)3(AlSi3O10)(OH,F)2

Composition: Basic potassium magnesium aluminum silicate, sometimes with some

iron and fluorine.

Crystal System: Monoclinic

Environment: In marble formed from metamorphosed limestone and dolomite.

Rock Type: Metamorphic

COMMON MINERAL ASSOCIATIONS:

Calcite, Diopside Chondrodite, Apatite, Graphite, Rutile.

X-RAY DIFFRACTION [By Intensity (I/Io)]: 9.998(1), 2.613(0.53), 3.382(0.33)

Biotite

Chemical Formula:

The classic formula for Biotite is: K(Mg,Fe2+3)(Al,Fe3+)Si3O10(OH,F)2

The group formula including all member minerals:

K(Mg,Fe2+)3(Al,Fe3+)[(Al,Si)3O10](OH,F)2

Individual members are:

Phlogopite: KMg3AlSi3O10)(F,OH)2 9.998(1), 2.613(0.53), 3.382(0.33)

Siderophyllite: KFe2+2Al(AlSi2O10)(OH)2 3.367(1), 10.2(1), 2.644(0.8)

Eastonite: KMg2Al(AlSi2O10)(OH)2

Annite: KFe2+3AlSi3O10(OH)2

Fluorannite: KFe2+3AlSi3O10)F2

Tetraferriannite: K(Fe2+3Mg)(Fe3+,Al)Si3O10)(OH)2

Composition: Basic fluoro potassium, magnesium, iron aluminum silicate.

Crystal System: Monoclinic

Environment: Biotite is a common rock-forming mineral, and is especially noted in

metamorphic rocks such as schist and gneiss. It is also found in igneous rock such as

granites and rhyolites. Biotite is also the primary mica in rare earth pegmatites.

Rock Type: Igneous, Metamorphic

COMMON MINERAL ASSOCIATIONS: Orthoclase, Hornblende, Quartz, Albite,

Calcite, Magnetite, Apatite, Diopside, Almandine.

X-RAY DIFFRACTION [By Intensity (I/Io)]: 3.37(1), 10.1(1), 2.66(0.8)

Lepidolite

Chemical Formula: K(Li,Al)3(Si,Al)4O10(F,OH)2

Composition: Basic potassium lithium aluminum fluoro-silicate

Crystal System: Monoclinic

Environment: Lepidolite is restricted to high-lithium granite pegmatites.

Rock Type: Igneous

COMMON MINERAL ASSOCIATIONS: Quartz, Microcline, Tourmaline,

Spodumene, Amblygonite.

X-RAY DIFFRACTION [By Intensity (I/Io)]: 3.34(1), 4.99(0.75), 10(0.75)

Chlorite

Chemical Formula: Below is a simple formula encompassing the common members

of the Chlorite Group: (Mg,Fe,Li)6AlSi3O10(OH)8

The formula for the three most common individual group members are:

Cookeite: LiAl5Si3O10(OH)8

Clinochlore: (Mg,Fe2+)5Al2Si3O10(OH)8

Chamosite: (Fe2+,Mg)5Al2Si3O10(OH)8

Composition: Basic iron magnesium aluminum silicate

Crystal System: Monoclinic

Environment: Most often in metamorphic environments, especially in Serpentine deposits; also as a

secondary mineral in volcanic basalt and in hydrothermal replacement deposits.

Rock Type: Igneous, Metamorphic

COMMON MINERAL ASSOCIATIONS: Calcite, Albite, Orthoclase, Actinolite, Serpentine,

Talc, Quartz, Magnetite, Almandine.

Clinochlore

Chemical Formula: (Mg,Fe2+)5Al2Si3O10(OH)8

Composition: Basic iron magnesium aluminum silicate. May also contain small amounts of chromium

Crystal System: Monoclinic

Environment: Always an alteration mineral. Commonly in metamorphic environments, especially

in Serpentine deposits; also as a secondary mineral in hydrothermal replacement deposits.

Rock Type: Metamorphic

POLYMORPHS:

COMMON MINERAL ASSOCIATIONS: Calcite, Albite, Orthoclase, Grossular, Diopside,

Serpentine, Talc, Quartz, Magnetite, Almandine.

X-RAY DIFFRACTION [By Intensity (I/Io)]: 7.16(1), 4.77(0.7), 3.58(0.6)

Chamosite

Chemical Formula: (Fe2+,Mg)5Al2Si3O10(OH)8

Composition: Basic magnesium iron aluminum silicate

Crystal System: Monoclinic

Environment: As an alteration mineral of metamorphic iron deposits, but also as a

secondary mineral in igneous traprock environments and granite pegmatites.

Rock Type: Igneous, Metamorphic

POLYMORPHS: Orthochamosite (Fe2+,Mg,Fe3+)5Al(Si3Al)O10(OH,O)8

(Orthorhombic) 3.513(1), 7.04(1), 2.514(0.9), 1.552(0.7), 2.137(0.6), 1.765(0.4),

2.673(0.4)

COMMON MINERAL ASSOCIATIONS: Calcite, Albite, Orthoclase, Quartz, Magnetite,

Almandine.

X-RAY DIFFRACTION [By Intensity (I/Io)]: 3.52(1), 7.05(1), 2.52(0.9)