Most often, this sort of exchange happens when someone asks for a mosaic, and I tell them, I only have a silver mosaic at this time. So I show them a picture... oh they want one more white. Well... a silver mosaic isn't white.... it's silver... hence, silver mosaic.
So, let's go back a few steps. A mosaic is a genetically white w/ grey markings chinchilla. They can range from mostly white (called "predominantly white" in show terms), to more spotty ("mosaic"), to white with darker hairs peeking through ("white with dark guard hairs") to a mostly silver-ish animal ("silver"). The base coat is white... other than that, they really vary.
For example, this is a chin that I have marked as a silver mosaic:
On the other hand, this is what I would term a white mosaic:
Yes, he has some silverish pattern, but it's not over the whole body, and he definitely looks of more of a white white, than the previous chin.
They're both mosaics. This is where it can be super useful when people tell me, ok, they want a white white, with as little shading on it as possible. Now, I may not have that... but at least, based on that description, I know what they're looking for. Cause if you ask for a mosaic... the top one is a mosaic... whether it fits a specific person's definition of mosaic or not. This ends your education for the day. :)