( Streak ( ( ( refers ( to ( the color ) ) ) ( that ( ( a mineral ) ( ( gives off ) ( when ( it ( is ( in ( powered form ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Streak)) (VP (VBZ refers) (PP (TO to) (NP (DT the) (NN color))) (SBAR (IN that) (S (NP (DT a) (NN mineral)) (VP (VBZ gives) (PRT (RP off)) (SBAR (WHADVP (WRB when)) (S (NP (PRP it)) (VP (VBZ is) (PP (IN in) (NP (JJ powered) (NN form)))))))))) (. .)))
Streak refers to the color that a mineral gives off when it is in powered form.
(ROOT (S (NP (NP (DT The) (NN color)) (PP (IN of) (NP (NP (DT the) (NN powder)) (PP (IN of) (NP (DT a) (NN mineral)))))) (VP (VBZ is) (VP (VBN called) (NP (NN streak)))) (. .)))