Need help finding name/info on QUARTZ BUBBLES/ "CHAMONIS" from Brazil Plz?

Question

Can anyone tell me more information about- and proper spelling of- a rock/mineral from Brazil that is called (phonetically) "Chamoni" ?

I think it is also called a 'quartz bubble'.

It is a type of quartz that is rough underneath with dark rusty coloring, and the top is rounded. It makes sort of a magnifying dome, and it's clear except for the underneath.

Any information would be appreciated!