Typically white, gray, or brownish in color, nepheline often exhibits a greasy appearance, but may also display a vitreous luster. The cleavage of nepheline is poor and when the mineral is placed in acid, it produces a hazy frost of silica gel. This characteristic is responsible for the name of the mineral, which is derived from the Greek word for “cloud.” Nepheline is sometimes confused with quartz because of their comparable optical properties, but the minerals do not appear together in the same rocks.