Action-adventure pictures have a lamentable tendency toward mindlessness, but Edward Zwick's epic story has numerous virtues apart from suspense and spectacle. A sharp script by Charles Leavitt and C. Gaby Mitchell centers on diamond grubbing during the horrific 1999 civil war in Sierra Leone, and all three lead actors contribute strong performances. Leonardo DiCaprio earns the label "Brando-esque" as a mercenary from Zimbabwe (even if his part recalls Bogart's in Casablanca), while Jennifer Connelly as a principled journalist and Djimon Hounsou as a Mende fisherman struggling to recover his family are no less potent. If you substituted oil for diamonds, much of the story could be happening right now in the Middle East. R, 138 min. a Century 12 and CineArts 6, Chatham 14, Cicero ShowPlace 14, Crown Village 18, Davis, Ford City, Gardens 7-13, Lake, Lawndale, Norridge, River East 21, 62nd & Western, Webster Place.