( ( ( ( ( This ( may ( be ( ( the ( way streak ) ) ( ( is commonly ) ( taught ( to beginners ) ) ) ) ) ) ) , ) but ) ( ( the streak ) ( ( ( is ( ( the color ) ( of ( ( the ( powdered mineral ) ) ( -LRB- ( ( ( especially when ) ( viewed ( on ( a ( white surface ) ) ) ) ) -RRB- ) ) ) ) ) ) and ) ( ( can easily ) ( be ( obtained ( by ( ( crushing ( the mineral ) ) ( if ( it ( ( is ( too hard ) ) ( to ( obtain ( by ( rubbing ( on ( the ( unglazed porcelain ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (DT This)) (VP (MD may) (VP (VB be) (NP (NP (DT the) (NN way) (NN streak)) (SBAR (S (VP (VBZ is) (ADVP (RB commonly)) (VP (VBN taught) (PP (TO to) (NP (NNS beginners))))))))))) (, ,) (CC but) (S (NP (DT the) (NN streak)) (VP (VP (VBZ is) (NP (NP (DT the) (NN color)) (PP (IN of) (NP (NP (DT the) (ADJP (JJ powdered)) (NN mineral)) (PRN (-LRB- -LRB-) (SBAR (WHADVP (RB especially) (WRB when)) (S (VP (VBN viewed) (PP (IN on) (NP (DT a) (JJ white) (NN surface)))))) (-RRB- -RRB-)))))) (CC and) (VP (MD can) (ADVP (RB easily)) (VP (VB be) (VP (VBN obtained) (PP (IN by) (S (VP (VBG crushing) (NP (DT the) (NN mineral)) (SBAR (IN if) (S (NP (PRP it)) (VP (VBZ is) (ADJP (RB too) (JJ hard)) (S (VP (TO to) (VP (VB obtain) (PP (IN by) (S (VP (VBG rubbing) (PP (IN on) (NP (DT the) (JJ unglazed) (NN porcelain)))))))))))))))))))) (. .)))
This may be the way streak is commonly taught to beginners, but the streak is the color of the powdered mineral (especially when viewed on a white surface) and can easily be obtained by crushing the mineral if it is too hard to obtain by rubbing on the unglazed porcelain.
(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)))) (. .)))