  We find excellent agreement between tunneling and optical conductivity gap
values in superconducting granular aluminum films, up to the Metal to Insulator
transition. This behavior, in strong contrast with that recently reported in
atomically disordered samples for which the optical gap becomes smaller than
the tunneling gap, rules out disorder as being at the origin of the transition.
Rather, it confirms that it is of the Mott type. The large increase seen in the
strong coupling ratio is interpreted as a sign of a BCS to BEC cross over,
consistent with a Mott transition.
