Robuta

https://www.usgs.gov/publications/distinguishing-palagonitized-pedogenically-altered-basaltic-hawaiian-tephra Distinguishing palagonitized from pedogenically-altered basaltic Hawaiian tephra: Mineralogical and... Palagonitization is a common, but imperfectly defined process that greatly modifies the physical and chemical properties of glassy basaltic tephra deposited in... distinguishingpalagonitizedalteredbasaltichawaiian