I don't know what origin sodalite we have, but I would not compare Na instability with F migration inside Apatite. In apatite the F migrates inside and is a reversible process (the F which initially migrates to deeper, partially homogenize/diffuses back to surface in a few weeks/moths). In Sodalite the Na escapes to Vacuum and is irreversible. The speeds of changes during probing are also complete different. Apatite is slow, where Sodalite is extremely fast (just enough of few nA·s for Na content to be halved, where Apatite-F can take hundreds of nA·s). In sense of Na-to-vacuum leak comparable to Sodalite is Gagarinite. Na in albite is clearly much much better binned and compared to those is extremely stable (at low current, and low beam density).
Where could I buy such Amelia Albite (Europe)?