a mother-of-pearl bead
 a flat headpin 
 a 20mm pendant
 a 4mm ring
 extension chain
 very fine chain
 3mm and 4mm rings
 a spring ring clasp

An ultra-simple assembly, start by mounting the mother-of-pearl bead on the headpin and form the loop.

Tip: do not make the loop too small because the chain will need to slide through it.

Next, mount the pendant on a 4mm ring.

Cut a very fine chain piece about 45cm / 50cm. Adjust the size as you wish. Enlarge the links with a reamer to make attaching the rings easier. 

Thread the pendant and the bead onto the chain.

Then at the ends of the chain, place on one side the clasp with a 3mm ring and on the other side a 3cm piece of extension chain with a 3mm ring.

Beautiful creation!