Out of 29 questions closed in the past month, 23 were rock-identification questions. All of them were closed because the asker did not follow this very good guide on how to ask them. Those questions may be perceived to lower the quality of the site, to the degree that they have been proposed to be essentially banned altogether.
We have a boilerplate text that anyone can add as a comment before voting to close a rock-identification question as unclear:
Your question is getting close votes because it has insufficient information. Please read our guide for asking “Identify this rock” questions and  your question. If your question is put on hold but you improve it, the community can vote to reopen it.
To make our life easier, I propose that we add a custom close reason for such questions:
Elsewhere on the network, Graphics Design has a custom close reason that may be used with their font-identification questions:
"Please review our font-identification, critique requests, or style-identification requirements and provide the missing information so that your question is both answerable and useful to others."
I propose that to make our life easier and our site friendlier, we add a custom "close as off-topic" reason on Earth Science as follows:
Please review our rock identification guidelines to provide the missing information so that your question is both answerable and useful to new users.
There is no provision for a custom "closing as unclear" close reason, but we can adapt the how to ask page if we wish.