Geometry and symmetry of minerals .
     The bulk of the matter comprising the earth's crust exists as compounds of .
elements called minerals.  There are more than 3,000 naturally occurring inorganic .
minerals, many of which exist in solid forms of varying composition, not to mention .
the countless number of synthetic compounds that have been formulated. .
. .
Conventional mineral classification scheme .
     Mineralogists have attempted to bring order to this vast collection of diverse matter
by cross indexing minerals with the chief nonmetal or radical present and the type of
structure commonly exhibited by them.  Often elements and minerals grouped in this
way are very similar in appearance, behave similarly when treated chemically, and
occur under similar geologic conditions.
     The following table is an example of such a classification scheme.  In the left hand
column the elements and minerals are grouped by the chief non-metal or radical
present.  In the right hand column each group is subdivided by the type of structure
commonly exhibited by the group.  The name of the structure is derived from an
element or mineral of the subgroup that is most commonly identified with the
structure or exhibits it most clearly.


Structural type


Structure type

 Native metals    Halides (continued)  
   Au,Ag,Cu,Pb,Pt,Pd   gold    halite group  
   a-Sn   diamond      halite   halite
   a-Fe   bcc      sylvite     "  "
 Native nonmetals      fluorite   fluorite
   C (diamond)   diamond  Oxides  
   C (graphite)   hp    periclase group  
 Sulfides        periclase   halite
   cinnabar   zincblende      bunsenite     "  "
   greenocite   wurtzite      manganosite     "  "
   galena group      zincite group  
     galena   halite      zincite   wurtzite
     altaite    "    "      bromellite    "      "
     clausthalite    "    "    cuprite   cuprite
     albandite    "    "    corundum group  
     oldhamite    "    "      corundum   corundum
   sphalerite group        hematite      "      "
     zincblende   zincblende      ilmenite      "      "
     metacinnabar      "       "    spinel group  
     tiemannite      "       "      spinel   spinel
     coloradoite      "       "      gahnite    "   "
   molybdenite group        hercynite    "   "
     molybdenite   molybdenite    magnetite   spinel  (inverse)
     tunstenite      "         "    rutile group  
   argentite group        rutile   rutile
     argentite   anti-flourite      pyrolusite    "  "
   chalcopyrite group        cassiterite    "  "
     chalcopyrite   zincblende      plattnerite    "  "
     stannite      "       "    urraninite group  
   niccolite group        urraninite   flourite
     niccolite   niccolite      thorianite     "    "
     pyrrhotite     "     "     (def.)    diaspore group  
     breithuptite     "     "      diaspore   diaspore
   skutterudite group        goethite      "     "
     skutterudite      brucite group  
 Sulfosalts        brucite    CdI2
   enargite group        pyrochroite      "
     enargite   enargite      portlandite      "
 Halides      boehmite  
   nantokite   zincblende      lepidocrocite   boehmite
   marshite      "       "    litharge   PbO
   miersite      "       "    


Table 3 -  Conventional mineral classification system


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Page  38 -  Structure matters - Minerals

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