▁Is ack ▁ground , ▁and ▁work ▁continued ▁until ▁the ▁ 1 9 5 0 s . ▁The ▁stone ▁in ▁question ▁was ▁intr us ive ▁bodies ▁of ▁mel ap hy re ▁covered ▁in ▁sed iment ary ▁depos its ▁such ▁as ▁sand stone , ▁sh ale ▁and ▁carbon ace ous ▁sh ale . ▁On ▁a ▁ring ▁about ▁ 2 0 0 ▁to ▁ 3 0 0   m ▁across ▁running ▁round ▁the ▁intr us ive ▁body ▁were ▁once ▁found ▁sand stone ▁quar ries . ▁This ▁shows ▁that ▁the ▁hot ▁mag ma ▁masses ▁were ▁thrust ▁as ▁high ▁as ▁this ▁only ▁in ▁this ▁area , ▁while ▁nearby ▁they ▁settled ▁into ▁layers ▁farther ▁below . ▁When ▁this ▁intr usion ▁happened ▁is ▁still ▁not ▁known . ▁The ▁age ▁of ▁the ▁surrounding ▁Rot lie g end ▁layers , ▁however , ▁is ▁known ▁to ▁be ▁roughly ▁ 2 4 0 , 0 0 0 , 0 0 0 ▁years . ▁ ▁Education ▁At ▁an ▁au ction ▁of ▁church ▁property ▁in ▁ 1 7 1 2 , ▁citizens ▁of ▁the ▁so - called ▁H ü ff l ert al ▁( H ü ff ler , ▁Sch ell we iler ▁and ▁W ahn w egen ) ▁acquired ▁plots ▁of ▁land ▁in ▁the ▁H ü ff ler ▁municipal ▁area ▁to ▁be ▁able ▁to ▁keep ▁a ▁school master ▁to ▁teach ▁the ▁children . ▁From ▁this ▁time ▁on wards , ▁there ▁was ▁a ▁school ▁for ▁these ▁three ▁villages . ▁In ▁ 1 7 1 5 , ▁thirty ▁children ▁were ▁att ending ▁school . ▁Begin ning ▁in