What common mineral's name (technically silica or SiO2) derives from old Polish-German 'kwardy', meaning 'hard'?
Rose quartz Citrine topaz Fruit quartz Citrine Rock crystal Blue quartz Citrintas Rock-crystal Star Blue Quartz Quartz Citrine quartz Quarz Bristol stone SiO2 Group Citrines Quartz crystals Bristowe stone Quartz (mineral) Rock-Crystal Milky quartz Star blue quartz Milk quartz Conite Quartz sand Quartz crystal Rock Crystal Blue Quartz Milky Quartz
rose quartz conite citrine topaz milky quartz citrine quartz quarz citrines star blue quartz quartz crystal citrintas quartz mineral rock crystal quartz sand bristol stone sio2 group fruit quartz bristowe stone milk quartz blue quartz citrine quartz quartz crystals
quartz
WikipediaEntity
Quartz