A 'grain' of developed silver looks like nothing so much as a bit of steel-wool scouring pad. The undeveloped silver halide crystal is either a cube (sometimes with itty-bitty cubes at the corners) [traditional emulsion] or a flat triangle with the points chopped off [t-grain 'tabular' emulsion]. The action of the developer is to extrude a filament of metalic silver from the active site on the exposed crystal. The shape of the developed silver filament has little, if anything, to do with the shape of the silver halide crystal.