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Numerical models of granular shear show lower friction and a greater tendency for stick slip than laboratory studies designed to investigate fault mechanics. Here we report on laboratory experiments designed to reproduce the conditions of numerical models and to test the role that grain characteristics play in controlling frictional behavior. Friction and microstructural data are compared for direct shear experiments on thin layers (2–3 mm) of angular quartz sand and spherical glass beads. We study the effect of grain shape, roughness, size distribution, and comminution. In a nonfracture loading regime, sliding friction for smooth spherical particles (μ ∼ 0.45) is measurably lower than for angular particles (μ ∼ 0.6). A narrow particle size distribution (PSD) of spherical beads (105–149 μm) exhibits unstable stick‐slip behavior, whereas a wide PSD of spheres (1–800 μm) and the angular gouge display stable sliding. At …