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Dimorphism, Trimorphism, Polymorphism

 

Dimorphism is the property of certain minerals to have the same chemical formula but they are crystallized in two different crystal systems. An example of dimorphism are Calcite  and Aragonite. Both have the chemical formula of CaCO3 but Calcite is trigonal and Aragonite is orthorhombic. The two minerals have the same chemistry, but have different crystal structures. They are said to be dimorphs of each other.

And of course, Trimorphism is the property of the same chemical compound to crystallize in one of three different crystal structures. A good example of trimorphism are Andalusite, Kyanite and Sillimanite. All three have the same basic chemistry, Al2SiO5, but Andalusite is orthorhombic, Kyanite is triclinic and Sillimanite is orthorhombic.

Polymorphism is the case of four or more minerals having the same basic chemistry but having different crystal structures.

Dimorph Minerals  

  • Boracite (orthorhombic) :: Trembathite (trigonal)
  • Catapleiite  (monoclinic) :: Gaidonnayite (orthorhombic)
  • Cavansite (orthorhombic) :: Pentagonite (orthorhombic)
  • Cordierite (orthorhombic) :: Indialite (hexagonal)
  • Cubanite (orthorhombic) :: Isocubanite (isometric)
  • Natrolite (orthorhombic) :: Gonnardite (orthorhombic)
  • Phosphosiderite (monoclinic) :: Strengite (orthorhombic)
  • Pyroxmangite (triclinic) :: Rhodonite (triclinic)
  • Kurnakovite (monoclinic) :: Inderite (triclinic)
  • Lepidocrocite (orthorhombic) :: Goethite (orthorhombic)
  • Zircon (tetragonal) :: Reidite (tetragonal)
  • Zoisite (orthorhombic) :: Clinozoisite (monoclinic)


Trimorph and Polymorph Minerals

  • Anatase (tetragonal) :: Brookite (orthorhombic) :: Rutile (tetragonal)
  • Andalusite (orthorhombic) :: Kyanite (triclinic) :: Sillimanite (orthorhombic)
  • Anorthite (triclinic) :: Dmisteinbergite (hexagonal) :: Svyatoslavite (orthorhombic)
  • Aragonite (orthorhombic) :: Calcite (trigonal) :: Vaterite (hexagonal)
  • Forsterite (orthorhombic) :: Ringwoodite (isometric) :: Wadsleyite (orthorhombic)
  • Diamond (isometric) :: Chaoite (hexagonal) :: Graphite (hexagonal) :: Lonsdaleite (hexagonal
     
     

 


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