The term 'mineral rarity' can be summarized as a crossword solution with the word 'GEM' being three letters. A GEM is a precious or semi-precious stone that is cut and polished for use in jewelry. Gems are usually rare and valuable due to their beauty, durability, and scarcity. Minerals are naturally occurring substances that form the basis of rocks and other geological formations. Mineral rarity refers to the scarcity of certain minerals, which makes them more valuable and sought after.