Marble is a rock which derives its name from Greek for 'crystalline rock' or shining stone. Pure white marble comes from pure limestone. However, coloured veins or swirls indicate the presence of clay, silt, sand, iron oxide, chert or serpentine (green colour (cf. Wikipedia on line). Marble was commonly used for headstones to engrave writing during the Mameluke and Ottoman eras, given its ability to withstand temperature, humidity and weathering.