The rust stains on the marble may be attributed either to the impurities in the marble stone itself or to external factors such placing of iron or metal objects on the marble surface. Marble being a natural stone, has impurities in the form of mineral deposits including iron. Over a period of time or even due to exposure to water, the iron in the marble oxidizes and it bleeds through to the surface, leaving a discoloured mark on the stone. These stains can be identified as orange-yellow-brown coloured discoloration on the stone surface. This type of rust is difficult to eradicate and needs the services of a marble restoration professional. Though, there can be no guarantee that the discoloration in the form of rust may not occur again.