Volcanic Rock

When we talk about volcanic rocks which are now gemstones we are primarily talking about an erupted lava which has within or has become a gemstone through deposition, weathering and alteration. 

When the gemstone is removed or weathers out like peridot or oregon sunstone we classify these on their own. This section is for rocks which we use in jewelry or carvings. 

Almost all lavas which erupt on the surface of the earth have some varieties used as gemstones.