SWEETGUM SG .52. Diffuse-porous. Good bows have been reported.
SG = weight of mass (in grams) / volume of mass (in cubic cm)
That's what I found on a list that Tim Baker has posted on potential bow woods. Here are some other examples that should give you a general comparison.
OAKS: California black .57; southern red .59; northern red, sessil, pin, bur .63; scarlet .67; white .68
OSAGE .82