Zeolite occurrences are common in volcanic rocks of Eocene age in the Fraser River area. These rocks are correlative with the Kamloops Group east of the Fraser fault; to the west of the fault the volcanic strata have not been formally named.

Zeolite deposits, accompanied by the development of bentonite, are formed by hydrothermal alteration of Eocene volcanic and sedimentary rocks. The proximity of many of these occurrences to the Fraser fault suggests that this and associated faults provided channelways for the passage of hydrothermal solutions.

Samples were taken at the northeastern end of a zeolitized rhyolite tuff. Heating the samples for 16 hours at 525 degrees indicates that the zeolite is an intermediate composition in the heulandite-clinoptiloite series. Exchangeable cation analyses yield, expressed in milli-equivalent per 100 grams: calcium, 42.50; magnesium, 2.75; sodium, 29.25; and pottasium, 8.50. The cation exchange capacity (CEC) is 82.1 (Open File 1988-29).