Back-scattered electron microscopy was used to study mineralization levels of human iliac cancellous bone of white females (N = 49). Mineralization levels were assessed by converting bone pixel grayscale levels to atomic number (Z) using known calibration standards. The data set consisted of bone biopsies from normal and vertebral fracture subjects that had either high or low values for bone formation rate (BFR_s) within their respective groups (fracture/low BFR_s, N = 12;​ fracture/high BFR_s, N = 10;​ normal/low BFR_s, N = 12;​ normal/high BFR_s, N = 15). The following three measures of mineralization were quantitatively determined for each specimen:​ an overall mean mineralization (Z_mean), the mineralization of trabecular packets deep within the interior of trabeculae (Z_deep), and the mineralization of superficial exterior packets (Z_superficial). Two-way analysis of variance revealed that the high BFR_s group had a significantly lower Z_superficial than the low BFR_s group [mean (SD) 10.383 (0.270) vs. 10.563 (0.289)], and there was no significant interaction. BFR_s had no effect on Z_mean or Z_deep. For the pooled data, Z_deep was significantly higher than Z_superficial [10.866 (0.242) vs. 10.471 (0.291)]. There was no significant difference in Z_mean, Z_deep, or Z_superficial between normals and those with vertebral fracture, but the standard deviations of the mineralization measures in the fracture group were at least double that of the normal group. Frequency histograms show that the two groups have fundamentally different mineralization distributions. The normal group demonstrates typical Gaussian distributions centered around the mean, and the distributions of the fracture group are bimodal, with peaks occurring at either the high or low tails of the distributions of the normal group. We hypothesize that both low and high patterns of mineralization might detrimentally affect bone material properties, with low mineralization levels causing reduced stiffness and strength and high mineralization resulting in reduced fracture toughness. The degree to which the mineralization differences may affect strength and stiffness of individual elements is estimated. The higher standard deviations of mineralization measures in the fracture group may reflect an inability to properly regulate trabecular level stress and strain. Forward stepwise regression analysis showed significant relationships between Ob.S/OS and both Z_superficial and Z_mean, suggesting that the osteoblast may play an important role in regulating mineralization.