Real Jet is very light and is a type of coal.Older jewellery tends to be chipped or cracked as Jet is quite fragile and was often carved Intricately.
If you put a drop of water on real jet it should absorb it.French Jet which is faceted glass will not absorb water and is much heavier than real jet. Other jet replica beads can be plastic or resin and can usually be spotted by looking for lines from the manufacture.
This is a false jet necklace.
