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Consider a quantity of sand gathered from a river bank. If you melt this in a furnace, then the source materials will be well mixed, and able to form what associations they may.

If you then allow this to cool gradually, then the minerals which have the strongest bonds AND which have the highest freezing point, will crystallize out first.

As the temperature continues to lower slowly, the minerals which have the next lowest freezing point AND the next strongest chemical bonds, these will crystallize out next. And so on.

The pressure within the body will also have an effect on the reactions that are possible. So, chemical valence, temperature, pressure, and time all have effect on the mineral formed.

In a real molten rock assembly, the micas will be among the last to crystal out. Their date of formation is often taken as the time of that thermal event which originally melted the rocks.

In situ, many minerals deposit out from a water solution, the stalactites in a cave are one low temperature example.

In a liquid of molten quartz and water, at high pressure and a temperature of several hundred degrees, then gold will be dissolved, and will precipitate out when the temperature OR the pressure drop sufficiently.

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11y ago

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