To me this looks like chalcedony with some agate formation. To be an agate it must technically be 50 percent agate. Interestingly, the agate and chalcedony are identical being a silicate.(SiO2). They feel smooth because they are microcrystalline, very small crystal structure. Quartz feels rough comparatively, even though it is SiO2 because it is macrocrystallinear. The waxy feel you get from chalcedony and in agates is because of that trait.
They are both very hard, If you try to scratch them they will not be scratched by a common household nail. There will usually not be a crack in them, the rock tends to chip out (like the upper right corner in your picture) in what are called conchoidal fractures, like the flint arrow heads. Also flint is a silicate and chert. All of then are SiO2.
I have no idea of its value, but I would buy it.