According to Karklins (cited previously), there are two common methods of heat rounding or "a speo". One, the bead with very sharp and sometimes jagged edges, from being chopped off the cane is placed on a spit and inserted into a "glory hole" in an oven where it is rotated and eventually removed to cool. The other method is: the beads are placed in a "frying pan" with a mix of ash and sand, then placed into furnace where the contents is stirred until the segments are sufficiently rounded. The reason is not always to get a rounded shape but in my opinion to "knock down" the sharp edges as to prevent cutting the cordage used in stringing these beads.
Also many "green/white/yellow hearts" are and were used by the Krobos and other African cultures in the decoration of powdered glass beads. I have witnessed many "Hengme", "Bodom" and "Akoso" types with decorations consisting of "melted green-hearts". I don't have any examples handy right now but I believe Carl can help here! If not there are many examples in the "search" section.
Thomas
P.S. the "Hengme" "Bodom" illustrated in thelink has older white hearts as the original dots in the decoration and newer white hearts as the repaired decoration.