tholeiite
noun
tho·lei·ite ˈtō-lə-ˌīt 
ˈthō-
ˈthō- : a basaltic rock that is rich in aluminum and low in potassium, is found typically in the ocean floor, and is probably derived from the earth's mantle
tholeiitic
ˌtō-lə-ˈi-tik
adjective ˌthō-
Word History
Etymology
German Tholeiit, from Tholey, village in Saarland, Germany + German -it -ite
First Known Use
1866, in the meaning defined above