SiO2-Y, an intermediate product of the transformation of silica gel to quartz, was synthesized from KOH or NaOH solution containing SiO2 and NaCl with a molar ratio of SiO2:H2O:Na+:OH- equal to 1:100:2-4:0.5 at 100-180 °C. In almost all reaction processes, SiO2-Y appeared asthe first crystal phase and then was transformed into SiO2-X2, cristo-balite, and finally quartz. The characterizations based on the chemical and physical data for SiO2-Y showed that SiO2-Y is magadiite (Na2Si14O29xH20, x = 9–11), which was discovered at Lake Magadi (an alkali lake), Kenya, and has been considered to be animportant precursor of inorganic bedded cherts.

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