Final answer:
The chemical formula that represents the composition of a mineral that usually exhibits fracture is (Fe, Mg)2SiO4.
Step-by-step explanation:
Minerals that exhibit fracture, rather than cleavage, break irregularly along planes that don't have weak chemical bonds. Fracture can occur on mineral surfaces that may appear flat, but they are not cleavage planes. The chemical formula that represents the composition of a mineral that usually exhibits fracture is (Fe, Mg)2SiO4.