Q. Is quartz a crystal or stone?

Answer

At temperatures below 573 °C (846 K; 1063 °F) quartz belongs to the trigonal crystal system. Above this temperature however it belongs to the hexagonal crystal system. The perfect shape for a crystal would be a prism with six sides that tapered out into pyramids with six sides at either end. Quartz has been the subject of study since ancient times; the ancient Greeks referred to crystals with a transparent appearance as krystallos which is where the word crystal or more frequently rock crystal comes from when referring to this type of quartz. In 1530 Georgius Agricola was the first person to use the name "quartz" which is an ancient German word of unknown provenance.