Water and mercury are often classified as mineraloids. They are the only two natural inorganic substances that have a definite chemical composition and are liquids at room temperature. They are also the only two liquids that crystallize into minerals within the range of temperatures and pressures encountered at Earth’s surface. Water crystallizes into the mineral “water ice” when cooled to 0 degrees C. Mercury crystallizes into solid mercury at -38.8 degrees C. Due to the fact that they crystallize into minerals, some mineralogists include water and mercury in the mineraloids group.