als ▁around ▁a ▁foss il , ▁a ▁con cret ion , ▁is ▁responsible ▁for ▁the ▁out standing ▁pres ervation ▁of ▁many ▁am mon ite ▁foss ils . ▁ ▁When ▁am mon ites ▁are ▁found ▁in ▁cl ays , ▁their ▁original ▁mother - of - pe ar l ▁co ating ▁is ▁often ▁preserved . ▁This ▁type ▁of ▁pres ervation ▁is ▁found ▁in ▁am mon ites ▁such ▁as ▁Hop l ites ▁from ▁the ▁C ret ace ous ▁G ault ▁cl ay ▁of ▁Fol k estone ▁in ▁Kent , ▁England . ▁ ▁The ▁C ret ace ous ▁Pierre ▁Sh ale ▁formation ▁of ▁the ▁United ▁States ▁and ▁Canada ▁is ▁well ▁known ▁for ▁the ▁abund ant ▁am mon ite ▁fa una ▁it ▁yields , ▁including ▁Bac ul ites , ▁Pla cent ic eras , ▁Sc aph ites , ▁Hop los cap h ites , ▁and ▁Je let z ky tes , ▁as ▁well ▁as ▁many ▁un co iled ▁forms . ▁Many ▁of ▁these ▁also ▁have ▁much ▁or ▁all ▁of ▁the ▁original ▁shell , ▁as ▁well ▁as ▁the ▁complete ▁body ▁chamber , ▁still ▁int act . ▁Many ▁Pierre ▁Sh ale ▁am mon ites , ▁and ▁indeed ▁many ▁am mon ites ▁throughout ▁earth ▁history , ▁are ▁found ▁inside ▁con cret ions . ▁ ▁Other ▁foss ils , ▁such ▁as ▁many ▁found ▁in ▁Mad agas car ▁and ▁Al berta , ▁display ▁ir ides c ence . ▁These ▁ir ides cent ▁am mon ites ▁are ▁often ▁of ▁gem ▁quality ▁( amm ol ite ) ▁when ▁pol ished . ▁In ▁no ▁case ▁would