The pilot of the tailwheel-equipped airplane reported that, during the approach to land on a private, gravel-covered airstrip, a dust cloud obscured three-quarters of the airstrip, but the approach end of the airstrip remained visible. He added that, during the approach, the airplane encountered wind shear, and the main landing gear then impacted terrain before the approach end of the airstrip. The airplane then bounced and came to rest nose down. The airplane sustained substantial damage to the landing gear box. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation. The pilot reported that, about the time of the accident, the wind was variable from 060° to 120° at 20 knots, gusting to 25 knots. The pilot landed the airplane to the east.