The crossword solution for the term 'clear mineral, eg, quartz' is 'CRYSTAL'. A CRYSTAL is a solid material composed of atoms or molecules that are arranged in an orderly repeating pattern. Crystals are found naturally in many different forms and can be made artificially in a laboratory. Quartz is one of the most common minerals on Earth and is composed of silicon dioxide. It is often used in jewelry and other decorative items due to its clarity and sparkle.