An important early material, obsidian, was discovered on the island of Milos.
( ( ( ( ( An ( important ( early material ) ) ) , ) obsidian ) , ) ( ( was ( discovered ( on ( ( the island ) ( of Milos ) ) ) ) ) . ) )
(ROOT (S (NP (NP (DT An) (JJ important) (JJ early) (NN material)) (, ,) (NP (NN obsidian)) (, ,)) (VP (VBD was) (VP (VBN discovered) (PP (IN on) (NP (NP (DT the) (NN island)) (PP (IN of) (NP (NNP Milos))))))) (. .)))
They discovered obsidian in Africa.
( They ( ( ( discovered obsidian ) ( in Africa ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBD discovered) (NP (NN obsidian)) (PP (IN in) (NP (NNP Africa)))) (. .)))