The BIG BEND diatomite deposit is located on Lot 6182 along the east side of the Fraser River on the southern edge of the Big Bend, 8 kilometres north-northwest of Quesnel. The largest diatomite deposits in British Columbia occur in this area.
Several exposures of pale buff to white diatomite occur in cliffs of the Fraser River over disrupted north-south lengths, constituting what is referred to as the Crownite Formation. The diatomite lies on a bed of light-grey clay below which is a thick sequence of sand, gravel, clay and some volcanic ash.
The Late to Middle Miocene Crownite Formation is a recessive and poorly exposed lacustine diatomite with the occasional clay/mudstone interbed. Quaternary glacial till and related colluvium overlie the Crownite Formation. The Lower to Middle Miocene Fraser Bend Formation sands, gravel and clays, underlying the diatomite beds have been affected by extensive block sliding, making it difficult to estimate exact thicknesses of the diatomite beds. The diatomite consists almost exclusively of various sizes of Melosira granulata diatoms, usually very small, with variable amounts of clay, silt and volcanic ash. The diatomite ranges in colour from white to grey to buff.
There are three major exposures of diatomite on Lot 6182. Small lots of the diatomite have periodically been shipped to Vancouver for making insulating brick.
A 3 to 6 metre bed of white stoneware clay underlies the diatomite. The deposit occurs close to water level at the downstream end of the big bend. The clay is interstratified with other clay and sandstone members of the Tertiary Fraser River series and is exposed for about 440 metres along the river. The clay deposit is on average 3 to 3.5 metres thick and dips gently to the south.
A sample of the clay had good plasticity and dried safely at 85 degrees Celsius. It fired to a hard cream body at cone 2, had a softening point at cone 16 and was classified as suitable for the production of sewer-pipe, flue-linings etc.
See QUESNEL (L.12194) (Minfile 093G 046) for more detailed information on the diatomite beds.
