The answer is "Yes". Although the spell description for the
scrying spell does not explicitly state you can scry on objects, we can imply
the spell, and crystal balls, were intended to be included based on the description
of several other spells, most notably Obscure Object and Nondetection. The text of each of those spells specifies
that they make it more difficult to scry upon objects or beings when using the
scrying spell or a crystal ball.
When scrying upon an
object, or person, there must be sufficient light for the scrier to see the
object being scried upon. If you attempt
to scry upon an object locked in a dark chest and you don't have darkvision, you
will be unable to see the object you are scrying upon, but you will know that
it is in a dark place.
