Quartz is the most widely mined stone in the world and also one of the most varied. Quartz is a silicate mineral made up of silicon and oxygen atoms in an octahedral arrangement. There are many varieties of quartz.
Geodes are nodular rocks that have formed in the cool, moist environment of a mineral-rich spring or cave. Usually found in arid climates, a few lucky people might stumble across one in their back yard. Although geodes look similar, each has its own unique characteristics.