Metal bead necklaces

Any thoughts on these please?
The darker one looks like Marcasite but large beads. Heavy and restrung or badly strung in the first place.
The lighter ones look like aluminium- definately lighter in weight but feel solid not hollow.
The indentations make me think they had or were meant to have glass gems in them but there is no sign of old glue. The clasp and stringing is throwing me off though as looks to have some age? Choker length. Thankyou for looking

 

Think I have answered myself that the darker one is Pyrite?

 

The light ones may be mercury glass.

 

Oh good, those’ll be the ones I just chinked on my teeth to test
Off to google mercury glass to see how long I’ve got left .

 

You won't die, would I lie to you!