Unmixing of solid solution phases

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Exsolution/unmixing (or oxy-exsolution in some cases) form as the solid solution mineral unmix upon cooling.

 

Terminology for alkali feldspar

  • Perthite – exsolution of Na-feldspar (blebs or irregular lamellae) inside K-feldspar

  • Antiperthite – exsolution of K-feldspar (blebs or irregular lamellae) inside Na-feldspar

 

Widmenstatten texture - Fe-Ni alloy

 

Fe-Ti oxides (oxy-exsolution) - to finish

  • Chalcosite-bornite – bornite forms triangular lattice of bladed crystals in chalcocite

  • Sphalerite-chalcopyrite (chalcopyrite disease) – blebs of chalcopyrite inside sphalerite (this is now considered as a replacement texture, not an exsolution)

  • Sphalerite exsolution inside chalcopyrite – rounded or cross-shaped, very specific

  • Chalcopyrite-bornite – blades of one in the other (depending which mineral predominates)

  • Chalcopyrite-cubanite – cubanite occurs as parallel laths or bands in chalcopyrite

  • Pyrrhotite-pentlandite – irregular lamellae, flame-shaped Ni-rich exsolutions