The effect of $alpha$/$eta$ phase on the mechanical properties and contact damage of silicon nitrides $Si_3N_4$) was investigated. Silicon nitride materials were prepared from two starting powders, at selective increasing hot-pressing temperatures to coarsen the microstructures: (i) from relatively coarse $alpha$-phase powder, essentially equiaxed $alpha$-$Si_3N_4$ grains, with limited, slow transformation to $eta$-$Si_3N_4$ grain; (ii) from relatively fine $alpha$-phase powder, a more rapid transformation to $eta$-$Si_3N_4$, with attendant grain elongation. The resulting micro-structure thereby provided a spectrum of $alpha$/$eta$ phase ratios, grain sizes, and grain shapes. Fracture strength, hardness, and toughness were measured, and contact damage and strength degradation after indentation were investigated by Hertzian indentation using spherical indenter. A brittle to ductile transition in $Si_3N_4$ depended on $alpha$/$eta$ phase ratio as well as grain size. Silicon nitride with elongated $eta$ grains showed a superior, contact damage resistance.