Quartz: synthesis at Earth-surface conditions.

Quartz has been crystallized directly from seawater at room temperature. This is the first time that identifiable quartz has been synthesized in aqueous solution at earth-surface conditions without the aging of an original amorphous precipitate. The concentration of dissolved silica in equilibrium with quartz at 20 degrees C and 1 atmosphere is 4.4+/-0.3 parts per million, a value in agreement with the theoretical value obtained by a constant heat capacity fit of higher temperature equilibrium data. This experiment confirms the results of petrologic investigations which suggest that quartz precipitates directly from aqueous solution during chemical weathering and early diagenesis.