John in NM
That explains the origin of the terms perhaps. These days the nomenclature is felsic for siliceous rocks and mafic for Mg-Fe rich, silica depleted rocks, intermediate between the two. I haven't heard the acid-base thing since taking a class from a professor who started at U of A when my dad went there
I also wonder if this has something to do with how quartz polishes so differently from other silicates.... just speculating of course, but it can be a tricky minderal to polish well. Cerium oxide on plexiglass is how it's typically done, which works well for a lot of silicates, but Alumina on tin works well for just about everything except quartz. Both methods clearly have a chemical action as much or more than abrasive, and it can be seen in what looks like a flow patter on a poorly done facet of quartz.