  Although chemical vapor deposition (CVD) is one of the preferred routes to
synthetic diamond crystals, a full knowledge of the point defects produced
during growth is still incomplete. Here we exploit the charge and spin
properties of nitrogen-vacancy (NV) centers in type-1b CVD diamond to expose an
optically and magnetically dark point defect, so far virtually unnoticed
despite an abundance comparable to (if not greater than) that of substitutional
nitrogen. Indirectly-detected photo-luminescence spectroscopy indicates a donor
state 1.6 eV above the valence band, although the defect's microscopic
structure and composition remain elusive. Our results may prove relevant to the
growing set of applications that rely on CVD-grown single crystal diamond.
