( ( ( ( The ( gangue ( , ( or non-useful ) ) ) ) , ) ( minerals ( in ( the veins ) ) ) ) ( ( was ( mostly ( ( quartz and ) carbonates ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN gangue) (, ,) (CC or) (NN non-useful)) (, ,) (NP (NP (NNS minerals)) (PP (IN in) (NP (DT the) (NNS veins))))) (VP (VBD was) (ADJP (RB mostly) (JJ quartz) (CC and) (JJ carbonates))) (. .)))
The gangue, or non-useful, minerals in the veins was mostly quartz and carbonates.
(ROOT (S (NP (DT The) (NN mineral) (NN quartz)) (VP (VBZ is) (VP (VBN used) (S (VP (TO to) (VP (VB produce) (NP (NN glass))))))) (. .)))