22 samples of opokas (porcellanites) of the Kamennoyarskoje deposit were examined by X-ray quantitative phase analysis. Mineral composition of opokas includes opal-CT-phase (34-86%), clay minerals (9-19%), quartz (3-15%), zeolite (0-17%), feldspar (0-5%). The proportion of opal, cristobalite and tridymite components in the diffraction profile of opal-CT-phase remains constant in all the studied samples. Hence, the formation of opokas of the Kamennoyarskoje deposit, consisting mainly of opal-CT - a natural silica polymer, took place continuously at constant physical and chemical environmental conditions. Two types of zeolites with varying degrees of confidence identified. Clinoptilolite is uniquely determined, Phillipsite - less confident, because its trace content. Smectite is present in small quantities and surely can not be diagnosed.
Keywords: flask, opal-CT phase, zeolite, smectite.