The crossword solution for the term 'GRANITE, CONSTITUENT OF' is MICA, which is a four-letter word. MICA is a group of silicate minerals that are composed of varying amounts of aluminum, potassium, magnesium, iron, and water. It is commonly found in granite, a type of igneous rock that is formed from cooled magma or lava. MICA is an important constituent of granite, as it helps to give the rock its unique texture and appearance.