You're essentially asking for a scope change. Just blacklisting/banning the tag won't help; users will simply use other tags (such as the country they've found the rock in, or even random tags) for their questions.
Scope changes should be discussed on the site's own Meta and Idea - make identification request posts off topic and I've had enough. Let's ban rock id questions seem a good start. If you can get enough support, you can turn it into a formal request to make all rock identification requests off-topic; then, the ♦ moderators can change the existing close reason
Please review our rock identification guidelines to provide the missing information so that your question is both answerable and useful to new users.
into something like
Identification questions are off-topic, because they tend to attract low-quality and low-effort posts. The community has decided to no longer support these questions. Please refer to [this meta post] for additional details. You may also check [this list] of external identification resources.
(borrowed from Movies & TV Stack Exchange; your site should provide appropriate links)
and the Help Center article What topics can I ask about here? should be updated by them as well.