Black Gum is an alternative name for Black Tupelo, a tree than grows in the southern United States.
This tree should not be confused with the Australian Gum trees which are some (but not all) of the many varieties of Eucalyptus that grow in that country.
Turning Black Gum
Black gum can have a dark tint to the wood which leave it with a muddy characteristic when turned and finished. It is not a highly desirable wood to make pens from.