Oh, and I thought of one more thing.
When a name has been accepted, people stray from it. So then who judges what range of marbles fits into that name?
I'm trying to remember an example where that became troublesome for me once. I think Vitro Opal was an example. I'm not sure but I _think_ that may be an example of where what one large group of collectors defined as opals ended up being different from what the people who came up with the name defined as opals.
If I'm wrong about that particular case, you can still see how that could happen. Definition shift.