The Phyllosilicate Subclass
(The Sheet Structures)
A subclass of the Silicates

In the Phyllosilicates, rings of tetrahedrons are linked by shared oxygens to other rings in a two dimensional plane that produces a sheet-like structure. Typically, the sheets are then connected to each other by layers of cations. These cation layers are weakly bonded and often have water molecules and other neutral atoms or molecules trapped between the sheets. This explains why this subclass produces very soft minerals such as talc, which is used in talcum powder. Some members of this subclass have the sheets rolled into tubes that produce fibers as in asbestos serpentine. The silicon to oxygen ratio is generally 1:2.5 (or 2:5) because only one oxygen is exclusively bonded to the silicon and the other three are half shared (1.5) to other silicons. The symmetry of the members of this group is controlled chiefly by the symmetry of the rings but is usually altered to a lower symmetry by other ions and other layers; but the overlying symmetry of the silicate sheets will usually still be expressed in a higher pseudo-symmetry. The typical crystal habit of this subclass is flat, platy, book-like and most all members display good basal cleavage. Although members tend to be soft, they are remarkably resilient. Members of this group are often the last to chemically breakdown in erosional and weathering processes and thus constitute a significant amount of soils and fine grained sedimentary rocks. This group is also generally tolerant of high pressures and temperatures and they make-up a large part of metamorphic rocks.

Below are the more common members of the phyllosilicates:
  • Allophane (Hydrated Aluminum Silicate)
  • Apophyllite (Hydrated Potassium Sodium Calcium Silicate Hydroxide Fluoride)
  • Bannisterite (Hydrated Potassium Calcium Manganese Iron Zinc Aluminum Silicate Hydroxide)
  • Carletonite (Hydrated Potassium Sodium Calcium Silicate Carbonate Hydroxide Fluoride)
  • Cavansite (Hydrated Calcium Vanadate Silicate)
  • Chrysocolla (Hydrated Copper Aluminum Hydrogen Silicate Hydroxide)
  • The Clay Group:
    • The Chlorite Group:
      • Baileychlore (Zinc Iron Aluminum Magnesium Silicate Hydroxide)
      • Chamosite (Iron Magnesium Aluminum Silicate Hydroxide Oxide)
      • The generallized mineral Chlorite
      • Clinochlore (Iron Magnesium Aluminum Silicate Hydroxide)
      • Cookeite (Lithium Aluminum Silicate Hydroxide)
      • Nimite (Nickel Magnesium Iron Aluminum Silicate Hydroxide)
      • Pennantite (Manganese Aluminum Silicate Hydroxide)
      • Penninite (Iron Magnesium Aluminum Silicate Hydroxide)
      • Sudoite (Magnesium Aluminum Iron Silicate Hydroxide)
    • Glauconite (Potassium Sodium Iron Aluminum Magnesium Silicate Hydroxide)
    • Illite (Hydrated Potassium Aluminum Magnesium Iron Silicate Hydroxide)
    • Kaolinite (Aluminum Silicate Hydroxide)
    • Montmorillonite (Hydrated Sodium Calcium Aluminum Magnesium Silicate Hydroxide)
    • Palygorskite (Hydrated Magnesium Aluminum Silicate Hydroxide)
    • Pyrophyllite (Aluminum Silicate Hydroxide)
    • Sauconite (Hydrated Sodium Zinc Aluminum Silicate Hydroxide)
    • Talc (Magnesium Silicate Hydroxide)
    • Vermiculite (Hydrated Magnesium Iron Aluminum Silicate Hydroxide)
  • Delhayelite (Hydrated Sodium Potassium Calcium Aluminum Silicate Chloride Fluoride Sulfate)
  • Elpidite [Hydrated Sodium Zirconium Silicate]
  • Fedorite [Hydrated Potassium Sodium Calcium Silicate Hydroxide Fluoride]
  • Franklinfurnaceite (Calcium Iron Aluminum Manganese Zinc Silicate Hydroxide)
  • Franklinphilite (Hydrated Potassium Manganese Aluminum Silicate)
  • Gonyerite (Manganese Magnesium Iron Silicate Hydroxide)
  • Gyrolite [Hydrated Calcium Silicate Hydroxide]
  • Leucosphenite [Hydrated Barium Sodium Titanium Boro-silicate]
  • The Mica Group:
    • Biotite (Potassium Iron Magnesium Aluminum Silicate Hydroxide Fluoride)
    • Lepidolite (Potassium Lithium Aluminum Silicate Hydroxide Fluoride)
    • Muscovite (Potassium Aluminum Silicate Hydroxide Fluoride)
    • Paragonite (Sodium Aluminum Silicate Hydroxide)
    • Phlogopite (Potassium Magnesium Aluminum Silicate Hydroxide Fluoride)
    • Zinnwaldite (Potassium Lithium Iron Aluminum Silicate Hydroxide Fluoride)
  • Minehillite [Hydrated Potassium Sodium Calcium Zinc Aluminum Silicate Hydroxide]
  • Nordite [Cerium Lanthanum Strontium Calcium Sodium Manganese Zinc Magnesium Silicate]
  • Pentagonite (Hydrated Calcium Vanadate Silicate)
  • Petalite [Lithium Aluminum Silicate]
  • Prehnite (Calcium Aluminum Silicate Hydroxide)
  • Rhodesite (Hydrated Calcium Sodium Potassium Silicate)
  • Sanbornite (Barium Silicate)
  • The Serpentine Group:
  • Wickenburgite (Hydrated Lead Calcium Aluminum Silicate)
  • Zeophyllite [Hydrated Calcium Silicate Hydroxide Fluoride]

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Much information for this page provided by the Mineral Database.

Popular Members of the Silicates Class


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