Gold leaf

I have a query regarding gold leaf on a painting.  Our gallery has
just purchased a painting done in 1996 supposedly painted with gold
leaf. There is a significant amount of discolouration taking place.
Upon enquiring from the artist whether it was really gold leaf we
were told it was definitely real gold leaf.  Therefore I am asking
two questions:

    1.  Does anyone know of a test that does not damage the work
        which will tell us whether in fact it is gold?

    2.  Has anyone any thoughts on what could be causing this
        discolouration and what if anything can be done about it?

Lynn Campbell
Conservator
Robert McDougall Art Gallery
Christchurch, New Zealand.

                                  ***
                  Conservation DistList Instance 10:13
                  Distributed: Thursday, July 25, 1996
                       Message Id: cdl-10-13-008
                                  ***