its essence the separator 10 includes a dam formed from a dam like partition 12 which divides a trough 20 into a first zone z1 and a second zone z2 the first zone receives input from an input conveyor 192 fig1 and includes an output conveyor 30 therewithin the other side of the dam 12 defines the second zone remote from the input and first zone conveyor 30 and includes a second conveyor 90 bark passing over the dam 12 is carried from the trough by the second zone conveyor 90 gravel is removed from the trough by the first zone conveyor 30 more specifically and with reference to fig1 through 3 the structure of the trough 20 can be explored in its essence the trough includes a bottom wall 2 formed as a substantially rectangular blank that includes a first pair of spaced parallel side edges and a second pair of spaced parallel end edges orthogonally related to the side edges these end edges communicate with upwardly extending side end walls 6 8 which diverge upwardly and outwardly to form an inverted isoceles trapezoid the trough 20 is completed by two side walls 4 each extending orthogonally upward from the bottom wall 2 between the end walls 6 8 a dam type partition 12 is medially interposed between the end walls 6 8 extending between the side walls 4 with a central portion.