The way an artist painted pearls reflects his ability to observing nature and his knowledge of contemporary optical theory. Moreover, the painterly execution may also be considered as an individual characteristic useful in distinguishing hands. In this work, we propose a set of image analysis techniques to analyze and measure spatial characteristics of the digital images of pearls, all relying on the so called spatiogram image representation. Our experimental results demonstrate good correlation between the new metrics and the visually observed image features such as smoothness of transitions between areas of different lightness, and the degree of realism of the visual appearance in the painting. In that sense, our results set the basis in creating a practical tool for art historical attribution and give strong motivation for further investigations in this direction.