Placer Gold Panning: Density Separation (2D)

This 2D companion strips the 3D sluice down to the physics that actually does the work: a side-view cross-section where every sand, clay, black-sand and gold grain is a real particle governed by Stokes drag, buoyancy-adjusted gravity along an inclined bed, and riffle-driven recirculation. Four sliders — water flow speed, sluice slope, riffle height and agitation — feed directly into the per-grain equations of motion, so recovery rate and concentrate grade respond exactly the way a real sluice operator's tuning would.