In a surface-coated cutting tool, a hard coating includes one or more layers. At least one layer thereof is a hard coating layer composed of a complex nitride or carbonitride layer of Al, Cr, and Si and satisfying (Al.sub.1-x-yCr.sub.xSi.sub.y)(C.sub.zN.sub.1-z) where x, y and z are atomic ratios and satisfy 0.1x0.4, 0.01y0.2, and 0z0.3, respectively. The hard coating layer contains particles including: less than 10 atomic % of non-metal components selected from C and N; and metal components selected from Cr, Al and Si. In the cross-section perpendicular to the tool body surface, the number ratio of oblate particles with an Al content of 50 atomic % or less, a long diameter of less than 0.5 m, and an aspect ratio of 2.0 or more is 90% or more with respect to the total number of the particles.

Polycrystalline compacts include smaller and larger hard grains that are interbonded to form a polycrystalline hard material. The larger grains may be at least about 33 times larger than the smaller grains. An interstitial material comprising one or more of a boride, a carbide, a nitride, a metal carbonate, a metal bicarbonate, and a non-catalytic metal may be disposed between the grains. The compacts may be used as cutting elements for earth-boring tools such as drill bits, and may be disposed on a substrate. A particulate mixture includes a first plurality of grains of hard material having a coating formed over the grains of hard material. The coating comprises at least one of a boride, a carbide, a nitride, a metal carbonate, a metal bicarbonate, and a non-catalytic metal. A second plurality of grains of hard material has a grain size at least 33 times larger than the first plurality.