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PHYLLOSILICATES

VIEWS: 6 PAGES: 2

									                                             PHYLLOSILICATES

Kaolinite--Al silicate (OH) H = 2 earthy odor sticks to tongue
      a clay mineral     white to gray unless colored by impurities
      Origin by weathering of feldspars and deposition as a sedimentary rock.
      Missouri's clay industry is centered in the Mexico, Missouri area; company is A. P. Green.

Montmorillonite--Al silicate (OH)
     Similar properties to kaolinite and can't be separated without X-ray work.
     Tends to form in more arid environments, especially from the weathering of volcanic ash; the principal
     clay in bentonite.
     A swelling clay; has industrial applications Swelling gives "popcorn weathering" surface on outcrops.

Serpentine--Mg silicate (OH) H = 3-5           green
      two varieties: antigorite - massive, green, waxy luster
                      chrysotile - fibrous, flexible, asbestiform
      Forms as an alteration product of Mg silicates, especially olivine.
      Makes up the monomineralic rock called serpentinite, which originates from hydrothermal alteration of
      ultramafic rocks, especially dunite.
      Antigorite has been used for building stone, "verde antique", which commonly has associated magnesite
      veinlets.
      Chrysotile is asbestos and the flexible fibers may be woven into fireproof clothing, etc. The uses are
      limited today, because of environmental health concerns. However, research shows that the amphibole
      asbestos minerals are much more dangerous than chrysotile asbestos.

Talc--Mg silicate (OH)      H = 1 (Mohs) white, gray, green, etc.      triclinic {001} perfect cleavage
       giving flexible folia and greasy feel    pearly luster
       Used in talcum powder and cosmetics, paint, paper, etc.
       Occurrence: metamorphic in talc schist; also as a hydrothermal alteration product of Mg-bearing rocks.

Muscovite--KAl silicate (OH) H = 2.5 monoclinic {001} perfect cleavage giving thin, elastic sheets
     colorless in thin sheets; various light colors in thicker pieces
     Common in igneous and metamorphic rocks; large crystals come from pegmatites.
     Also found in some sandstone sedimentary rocks; because of its great resistance to chemical attack it is
     able to survive the weathering cycle---small flakes are common in the Warrensburg Sandstone.
     Ground mica is used in wallpaper for the luster, as a filler in plastics, as fireproofing, in wallboard joint
     cement, paint, oil well muds, and rubber.

Phlogopite--KMgAl silicate (OH) H = 2.5 light to medium “reddish” brown        monoclinic
      {001} perfect cleavage giving thin, elastic sheets
      Distinguish from biotite by:
               -color in thin piece brown, not black
               -occurrence
      Occurrence: metamorphosed dolomite or magnesian limestone and in ultramafic igneous rocks,
      especially kimberlite pipes.
Biotite--KMgFeAl silicate (OH) H = 2.5         black color       monoclinic      perfect {001} cleavage giving
        thin elastic folia     weathers golden brown
        A very common rock-forming mineral in many types of igneous and metamorphic rocks; not usually
        found in sedimentary rocks because it doesn't survive the weathering process.

Vermiculite--Mg silicate (OH)       H = 1.5     brown to black   one perfect cleavage with flexible folia
      expands 10-15 times upon heating due to interlayered water
      uses: insulation (Zonolite), packing, soil conditioner
      mined at Libby, Montana and Macon, North Carolina; it is expanded after shipping.

Glauconite--KFe silicate (OH)    green    amorphous appearing
      an authigenic mineral in sedimentary rocks, especially carbonates and sandstones.
      identified by occurrence

Chlorite--MgFeAl silicate (OH)   H = 2.5      green color         monoclinic        {001} perfect cleavage
       giving flexible folia
       Occurrence: metamorphic rocks like chlorite schist; also in igneous rocks as a deuteric alteration
       product.

Lepidolite--KLiAl silicate (OH) H = 2.5-4 pink to lilac to greenish monoclinic {001} perfect cleavage
      Occurrence in Li-rich pegmatites associated with other lithium minerals such as spodumene and Li-
      tourmaline (rubellite).
      Muscovite can be the same colors as lepidolite; separate by lepidolite's fusibility of 2; muscovite is
      infusible.

Pyrophyllite--Al silicate (OH)   H = 1-2     {001} perfect cleavage     white, gray, greenish, brownish
      commonly in radiating masses.
      Has the same uses as talc, but not as desirable.

								
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