The lumps inside it look like what is called "goldstone" - when it's being described by folk who are into crystals.
I'm pretty sure it's glass containing copper specks - and what is used as Aventurine in glass making (as opposed to the green stone the crystal folk call aventurine.)
However, I don't know how it's made if it is glass containing copper specks - how does it not oxidise?
It can get very confusing.
You see bracelets and lumps of crystal on leather straps produced by crystal folk, who say it promotes good health or brings luck or whatever, and they have their names for certain semi-precious stones, then there are the real chemical names, the gemologists names etc.
Frankly, the whole weight looks like something fairly contemporary, probably from the far east, and is basically just lumps of goldstone shoved at the bottom of a lump of glass.
I can see no artistic merit in it at all, I can
easily imagine a whole stall of them at some new-age fair.
You can buy elastic bracelets of goldstone and other crystally things very cheaply in British Heart Foundation shops, I don't think it's confined to Murano.