This is a 6.8" wide, polished quartz bowl from Madagascar. This specimen has been polished into a large bowl, from a larger chunk of quartz. There are some spots of gap fill with the possibility of a repaired crack. This imperfection has been reflected in the price of the specimen.
Silicon Dioxide, also know as SiO2 or Quartz, is the second most abundant mineral in the Earth's crust. Quartz crystals generally grow in silica-rich, hot watery solutions called hydrothermal environments, at temperatures between 100°C and 450°C, and usually under very high pressure. Quartz veins are formed when open fissures are filled with hot water during the closing stages of mountains forming, and can be hundreds of millions of years old.