( a ( natural ( mineral ( rock ( salt . ) ) ) ) )
(ROOT (NP (DT a) (JJ natural) (NN mineral) (NN rock) (NN salt) (. .)))
a natural mineral rock salt.
(ROOT (S (NP (DT A) (NN mineral)) (VP (VBZ is) (VP (VBN described) (PP (IN as) (NP (NP (DT a) (JJ natural) (NN substance)) (SBAR (WHNP (WDT that)) (S (VP (VBZ makes) (PRT (RP up)) (NP (NNS rocks))))))))) (. .)))