Normally, if you hold something like a gold clasp and a copper clasp up to a bead you can easily tell if the inclusion or surface decoration is gold or aventurine (copper). It's sometimes hard to tell from pictures due to variations in color rendition.

Some of the "drizzle" on wedding cake beads is gold and some is aventurine. In general I think gold foil decoration is more rare but other forumites may be able to clarify that.