▁bas alt ▁describing ▁a ▁particular ▁composition ▁of ▁la va - der ived ▁rock ▁origin ates ▁from ▁its ▁use ▁by ▁Georg ius ▁Agr icola ▁in ▁ 1 5 5 6 ▁in ▁his ▁famous ▁work ▁of ▁min ing ▁and ▁min eral ogy ▁De ▁re ▁met all ica , ▁lib ri ▁XII . ▁Agr icola ▁applied ▁" bas alt " ▁to ▁the ▁vol can ic ▁black ▁rock ▁of ▁the ▁Sch lo ß berg ▁( local ▁castle ▁hill ) ▁at ▁St ol pen , ▁bel ieving ▁it ▁to ▁be ▁the ▁same ▁as ▁the ▁" very ▁hard ▁stone " ▁described ▁by ▁Pl iny ▁the ▁E lder ▁in ▁Natur alis ▁Historia e . ▁ ▁Types ▁▁▁ ▁Th ole i it ic ▁bas alt ▁is ▁relatively ▁rich ▁in ▁sil ica ▁and ▁poor ▁in ▁sod ium . ▁ ▁In cluded ▁in ▁this ▁category ▁are ▁most ▁bas al ts ▁of ▁the ▁ocean ▁floor , ▁most ▁large ▁ocean ic ▁islands , ▁and ▁contin ental ▁flo od ▁bas al ts ▁such ▁as ▁the ▁Columbia ▁River ▁Pl ate au . ▁High ▁and ▁low ▁tit an ium ▁bas al ts . ▁Bas alt ▁rocks ▁are ▁in ▁some ▁cases ▁class ified ▁after ▁their ▁tit an ium ▁( T i ) ▁content ▁in ▁High - T i ▁and ▁Low - T i ▁vari eties . ▁High - T i ▁and ▁Low - T i ▁bas al ts ▁have ▁been ▁distinguished ▁in ▁the ▁Par an á ▁and ▁E ten de ka ▁tra ps ▁and ▁the ▁E me ish an ▁Tra ps . ▁ ▁Mid - o cean ▁r idge