  The Vickers hardness of polycrystalline {\gamma}-B was measured using a
diamond indentation method. The elastic properties of polycrystalline
{\gamma}-B (B=213.9 GPa, G=227.2 GPa, and E=503.3 GPa) were determined using
ultrasonic measurement at ambient condition. Under the loading force up to 20
N, our test gave an average Vickers hardness in the asymptotic-hardness region
of 30.3 GPa. The average fracture toughness was measured as 4.1MPa m1/2.
Additionally, We also measured the hardness and elastic properties of
polycrystalline {\beta}-B and PcBN for comparison. The hardness and elastic
properties for polycrystalline {\gamma}-B was found to be very close to that of
PcBN. Our results suggest that the polycrystalline {\gamma}-B could be a
superhard polycrystalline material for industrial applications.
