  We explore the possible spectrum of binary mergers of sub-solar mass black
holes formed out of dark matter particles interacting via a dark
electromagnetism. We estimate the properties of these dark black holes by
assuming that their formation process is parallel to Population-III star
formation; except that dark molecular cooling can yield smaller opacity limit.
We estimate the binary coalescence rates for the Advanced LIGO and Einstein
telescope, and find that scenarios compatible with all current constraints
could produce dark black holes at rates high enough for detection by Advanced
LIGO.
