A polycrystalline compact comprising: a hard polycrystalline material comprising: a first region adjacent to a substrate comprising: (i) a first plurality of diamond grains having a first average grain size; (ii) a second plurality of diamond grains having a second average grain size smaller than the first average grain size, the diamond grains of the first plurality of diamond grains and of the second plurality of diamond grains being interspersed and inter-bonded; and (iii) catalyst material for catalyzing the formation of inter-granular bonds between the diamond grains of the first plurality of diamond grains and of the second plurality of diamond grains, the catalyst material disposed in interstitial spaces between the inter-bonded diamond grains of the first plurality of diamond grains and of the second plurality of diamond grains; and a second region disposed adjacent and directly bonded to the first region along an interface between the first region and the second region; the second region comprising a smaller volume percentage of diamond than the first region and comprising a third plurality of diamond grains having a third average grain size, the diamond grains of the third plurality of diamond grains being interspersed and inter-bonded, wherein interstitial spaces between the inter-bonded diamond grains of the third plurality of diamond grains are free of catalyst material for catalyzing the formation of inter-granular bonds between the diamond grains of the third plurality of diamond grains. a first region adjacent to a substrate comprising: (i) a first plurality of diamond grains having a first average grain size; (ii) a second plurality of diamond grains having a second average grain size smaller than the first average grain size, the diamond grains of the first plurality of diamond grains and of the second plurality of diamond grains being interspersed and inter-bonded; and (iii) catalyst material for catalyzing the formation of inter-granular bonds between the diamond grains of the first plurality of diamond grains and of the second plurality of diamond grains, the catalyst material disposed in interstitial spaces between the inter-bonded diamond grains of the first plurality of diamond grains and of the second plurality of diamond grains; and (i) a first plurality of diamond grains having a first average grain size; (ii) a second plurality of diamond grains having a second average grain size smaller than the first average grain size, the diamond grains of the first plurality of diamond grains and of the second plurality of diamond grains being interspersed and inter-bonded; and (iii) catalyst material for catalyzing the formation of inter-granular bonds between the diamond grains of the first plurality of diamond grains and of the second plurality of diamond grains, the catalyst material disposed in interstitial spaces between the inter-bonded diamond grains of the first plurality of diamond grains and of the second plurality of diamond grains; and a second region disposed adjacent and directly bonded to the first region along an interface between the first region and the second region; the second region comprising a smaller volume percentage of diamond than the first region and comprising a third plurality of diamond grains having a third average grain size, the diamond grains of the third plurality of diamond grains being interspersed and inter-bonded, wherein interstitial spaces between the inter-bonded diamond grains of the third plurality of diamond grains are free of catalyst material for catalyzing the formation of inter-granular bonds between the diamond grains of the third plurality of diamond grains.