I would like to know what phrasing is the correct geological technical term for a lode or ore vein that grows narrower and narrower till it narrows down to nothing - is it pinch out or peter out?
(besides, does it have to be geological technical term or geologically technical term or just geological term?)
Related: The lead has pinched right out
Yet again, you're being distracted by an outdated usage. There's merit in learning idiomatic peter out, because that's used metaphorically in a wide variety of contexts today. But not pinch out, which today only really exists in the sense of removing dead / unwanted parts of plants, and more recently the thumb+finger gesture used on touch screens to zoom the display. This really isn't relevant to "learning English". – FumbleFingers