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Incongruent melting

Incongruent melting occurs when a substance does not melt uniformly and decomposes into another substance. For example, potassium feldspar (KAlSi3O8) decomposes to leucite (KAlSi2O6) when it melts. The decomposition is not complete, however. Most of the feldspar does melt, a portion of it decomposes to leucite and some quartz (SiO2) is left over, since the chemical formulas of potassium feldspar and leucite differ by SiO2. Another mineral that melts incongruently is enstatite (MgSiO3), which decomposes to forsterite (Mg2SiO4). Enstatite does melt congruently between pressures of 2.5 and 5.5 kilobars.

See also


    This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Incongruent_melting". A list of authors is available in Wikipedia.
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