Definition
Variolites are a group of dark green basic igneous rocks which exhibit pale colored spots, or spherules, especially on weathered surfaces, that give them a pockmarked appearance
  
Rhyolite is a fine-grained igneous rock which is rich in silica
  
History
  
  
Origin
France
  
North America
  
Discoverer
Unknown
  
Ferdinand von Richthofen
  
Etymology
From Latin varius, speckled, variegated
  
From German Rhyolit, from Greek rhuax lava stream + lithos stone
  
Class
Igneous Rocks
  
Igneous Rocks
  
Sub-Class
Durable Rock, Hard Rock
  
Durable Rock, Hard Rock
  
Family
  
  
Group
Volcanic
  
Volcanic
  
Other Categories
Opaque Rock
  
Coarse Grained Rock, Opaque Rock