Definition: | crystal growth in the presence of water, elevated temperatures and pressures by a crystal growth process believed to proceed geologically within the Earth's crust Note 1 to entry: The industrial synthetic quartz growth processes utilize alkaline water solutions confined within autoclaves at supercritical temperatures (330 °C to 400 °C) and pressures (71 MPa to 203 MPa).The autoclave is divided into two chambers: the dissolving chamber, containing raw quartz chips at the higher temperature; the growing chamber, containing cut seeds at the lower temperature.
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