Black Whitby Jet Mourning Necklace

by ann
(united kingdom)

I wonder could you help I have aquired this long old black necklace To me it looks like Whitby Jet as I have black jet glass and there is no comparison.

The barrel clasp is enormous and shows a brown tinge at the end which makes me think it might be older than mourning jewelry. If you could help I would appreciate it thanks annmac