As a 0.6% C steel cools the ferrite precipitates out, and the remaining austenite phase become richer in carbon, until at 727oC the remaining austenite contains 0.8% carbon and forms pearlite defined in Samuels (2003, p25) as ” eutectoid transformation of ferrite and cementite with an ideally lamellar structure”. Samuels, L.E 2003 Light Microscopy of Carbon Steels. ASM International. The definitive text for carbon steels, an essential book for the metallography of steel (and ferritic iron). A quick look on Abe books, shows plenty of copies available but in USA/Canada