Spherical Graphite Natural Spherical Graphite One of the most unusual morphologies of graphite is that of spheres that have a radial texture in cross section. Such graphite has long been known to occur in certain cast irons but also occurs naturally in both igneous and metamorphic rocks.
Sizes range from microns to centimeters in diameter.
The microstructure of graphite aggregates are well revealed by reflected polarized light microscopy of polished sections. Click here to see polished sections of spheroidal aggregates from Sterling Hill. Graphite spheres from Sussex County, New Jersey Graphite spheres to 1cm in calcite matrix with franklinite. Probably from the Sterling Hill mine. E.W. Heinrich collection, Seaman Mineral Museum.