“The idea of stone and especially of precious stone is naturally fundamental to the rime petrose, which develop as their central motif the idea that the lady is a petra: as hard as a stone, but also as beautiful and as powerful as a precious stone. In Dante’s time, precious stones are believed to have powers deriving from the star or planet that fashioned them. As one might expect, this power is thought of as radiating invisibly from them; it is hidden, but its propagation is nonetheless thought of on the model of light. Dante writes of the influence of the donnapetra as if it were a kind of light proceeding in a straight line toward him from her, against which he has no shield; often it is implicitly or explicitly identified with the lady’s gaze. In “Così nel mio parlar” the metaphorics of light is exchanged for that of combat: the lady’s glance is like an arrow or a spear from afar; in the course of the poem this combat at a distance turns into hand-to-hand combat and finally into the act of love, which culminates in a return to the exchange of glances, this time the prolonged—and ultimately peaceful—mutual gaze of the lovers, finally reconciled, at least in fantasy…”
Source: Time and the Crystal: Studies in Dante’s Rime Petrose, by Robert M. Durling & Ronald L. Martinez. Berkeley: Univ. of California Press, c 1990. pp. 32-33.