( ( When ( lava ( cools ( very quickly ) ) ) ) ( , ( ( ( ( no ( crystals form ) ) and ) ( the rock ) ) ( ( looks ( ( shiny and ) glasslike ) ) . ) ) ) )
(ROOT (S (SBAR (WHADVP (WRB When)) (S (NP (NN lava)) (VP (VBZ cools) (ADVP (RB very) (RB quickly))))) (, ,) (NP (NP (DT no) (NNS crystals) (NN form)) (CC and) (NP (DT the) (NN rock))) (VP (VBZ looks) (ADJP (JJ shiny) (CC and) (JJ glasslike))) (. .)))
When lava cools very quickly, no crystals form and the rock looks shiny and glasslike.
(ROOT (S (NP (JJ Mineral) (NNS crystals)) (VP (VBP are) (VP (VBN formed) (SBAR (WHADVP (WRB when)) (S (NP (JJ hot) (NN lava)) (VP (VBZ cools)))))) (. .)))