Well, I've seen (and have examples somewhere..) this elongated shape nutshell carved into african-looking mask designs.
If I remember rightly the nut is Canarium ?something, and has a slightly triangular cross-section. I think your pendant might be one of these.

The various light-coloured flesh palm nuts that are carved and may be used as substitutes for ivory grow today in various tropical locations -they are ivory-coloured, with a dark skin -generally scraped or polished away.

Tagua nut is one, also Corozo palm nut.
They were widely used to make buttons too.
Lots of those carved beads in rough patterns come, or came in the 70's onwards, from Kenya. I still have a sackful.

Stefany