Honed Black Granite Hearth Custom Size No JointsSlab hearths or one piece hearths made from granite are suitable for electric, gas, bio ethanol, and bio electric fires. These appliances produce low levels of heat and do not require expansion joints, making slab hearths ideal. For stoves, slab hearths can only be used when the stove is not in direct contact with the hearthfor example, if the stove is mounted on legs that are at least 100mm high (depending on its kW output). For maximum heat