While browsing the tags, I noticed that we have limestone, but with only 20 questions. I've looked for other rock type tags, but couldn't find tags for the most common ones, e.g., sandstone, basalt, granite... (but each of those research terms yields > 100 questions).
Should we add the main rock types as tags, or else just remove limestone? (and other rock type tags, if any)
My suggestion: remove the limestone tag, and create three tags for the three main rock families:
Which could be made synonyms of existing tags sedimentology, igneous and metamorphism, respectively.