I liked this one!
From Publishers Weekly
Starred Review. In MWA Grandmaster Hillerman's sterling 17th Chee/Leaphorn novel, a 1956 collision between passenger planes high above the Grand Canyon leaves a courier's arm and attached diamond-filled security case unaccounted for after almost half a century. Enter retired Navajo Tribal Police Lt. Joe Leaphorn, who must try to connect the dots between an old robbery involving a valuable diamond and a more recent crime involving another diamond, both of which may somehow be related to the plane-crash jewels. The puzzle soon draws in fellow Navajo officer Sgt. Jim Chee and former cop Bernie Manuelito, Chee's soon-to-be bride. Billy Tuve, a cousin of Chee's lawman buddy Cowboy Dashee, is arrested after trying to pawn a gem believed to have come from the more recent robbery. Dashee enlists Chee's help to verify Tuve's story of a mysterious old man who gave him the jewel during a journey to a canyon-bottom shrine. But the good guys soon learn there are plenty more people in the hunt, and some will stop at nothing to get what they're after. The stakes are high and the danger escalates clear through to the final pages. Hillerman continues to shine as the best of the West.