Mineral, Chalcedony

Photo of a Chalcedony sample, which is a member of the group of quartz, collected in Tunisia in 1997. It appears in botryoidally aggregates in geoids. Outside, the geode is a moderate-sized stone and inside it is covered with crystals of Chalcedony. The chalcedony is a microcrystalline mineral crystal translucent to opaque. It has vitreous luster and the color is yellow to white-yellow. It has hardness of 7.