Estimating wear on bottom hole assembly (BHA) components utilizes a rock hardness index using analysis of drill cutting. Estimating the amount of wear on borehole assembly components comprises measuring the rock properties in drilled cuttings from a borehole. A hardness value is assigned to each mineral present in the drilled cuttings. A hardness index is calculated for a drilled borehole interval. A wear resistance factor is assigned to each BHA component of the BHA. The wear resistance factor depends on the wear resistance of each BHA component. A wear value for each BHA component is calculated based on the hardness index for the drilled borehole interval, the wear resistance of the BHA component, and drilling parameters.