Feldspar cement includes overgrowths on feldspar framework
grains (Figs. 62, 63) in all types of sandstones, which is by far t^a more common occurence, and also as a complete pore filling mosaic
of grains in arkose. Albite and K-spar are the only known cement
types, and both are extremely pure end members of the alkali and
plagioclase feldspar series (Kastner, 1971). Chemical conditions necessary for feldspar growth include a supply of dissolved silica
and high Na+/H+ or K+/Na+ activities such as might be found in
formation water of high salt concentration (Pettijohn and others,
1972, p. 429). The feldspars form at moderate burial depths and
are not of hydrothermal or metamorphic origin.