From David, Lehigh Acres
This is a species of Scleroderma. These are ectomycorrhizal fungi that form symbiotic relationships with some tree, particularly pines and oaks here in Florida, but also some other species (for example, we have one species that occurs with the sea grape, Coccoloba uvifera). Scleroderma are sometimes called “earthballs” and are related to other fungi known as “puffballs.” The expelled black dust particles are spores that have been released to colonize the roots of other oaks. There are about 25 species of Scleroderma and one would need a microscope to separate the species by examination of the spores. A symbiotic relationship is mutually beneficial to the organisms engaged in it. Therefore, no harm will come to your oak tree.