orbicule
noun
or·bi·cule
ˈȯ(r)bəˌkyül
plural -s
: a more or less spherical body found in some granites and other rocks, varying in size from a pellet visible only under the microscope to a sphere 10 feet or more in diameter, and having its constituents arranged in concentric shells
Word History
Etymology
Latin orbiculus small disk, diminutive of orbis disk, circle