Antique Green-Yellow-White Banded Jade? Hand-carved 11.5mm Bead 21" Necklace

This was purchased from a woman who claimed it was her grandmother's "jade" necklace.  It originally was strung with a hook clasp but ended up being replaced with a sterling silver tongue-in- groove clasp on the original string.
I am uncertain if Jade is banded or not, but the large banded bead stones appear to be hand-carved with a green-yellow tone; strung on the original string.  There are 48 beads total that measure 11.5 mm each that form a single strand.
The beads look natural and not treated.
Beads have a nice semi-glossy  luster.
The strand isx21" long.
A very classy beaded stone necklace.
Please view photos closely and discern for yourself what the stone might be.
There's about a 1/8" gap between string and beads.
Very good condition.  No chipped beads.
Selling "as is."