▁first ▁form ▁it ▁can ▁be ▁bed ded ▁in ▁a ▁ram sh ack le ▁manner ▁( as ▁rub ble ▁m ason ry ); ▁if ▁in ▁the ▁second ▁then ▁laid ▁in ▁courses . ▁ ▁In ▁either ▁case , ▁mort ar ▁is ▁often ▁used ▁between ▁stones ▁to ▁form ▁walls . ▁ ▁Properties ▁The ▁stone ▁is ▁a ▁ch alk ▁from ▁the ▁Lower ▁Ch alk ▁of ▁the ▁C ret ace ous ▁age , ▁the ▁period ▁of ▁ge ological ▁time ▁approximately ▁ 1 4 5 ▁– ▁ 6 6 ▁million ▁years ▁ago . ▁ ▁It ▁is ▁grey ish - white ▁to ▁light ▁be ige ▁in ▁colour , ▁often ▁with ▁a ▁green ish ▁t inge . ▁The ▁latter ▁is ▁due ▁to ▁the ▁presence ▁of ▁gla u con ite , ▁the ▁pot ass ium ▁and ▁iron ▁al umin ium ▁sil icate ▁min eral ▁that ▁is ▁also ▁found ▁in ▁Kent ish ▁R ag stone . ▁The ▁stone ▁has ▁a ▁g rit ty ▁texture ▁due ▁to ▁the ▁frequent ▁presence ▁of ▁shell ▁foss ils . ▁This ▁stone ▁has ▁been ▁quar ried ▁at ▁Tot tern ho e ▁Qu ar ry ▁in ▁D unst able , ▁Bed ford shire ▁by ▁H . ▁G . ▁Clar ke ▁& ▁Son ▁since ▁ 1 9 2 0 . ▁ ▁It ▁is ▁particularly ▁soft ▁when ▁quar ried ▁and ▁subject ▁to ▁chemical ▁and ▁wind ▁er os ion ▁as ▁exposed ▁material , ▁i . e . ▁when ▁un render ed ▁in ▁paint , ▁st u cco ▁or ▁c ement . ▁It ▁can ▁be ▁cut ▁by ▁a ▁saw ▁when ▁in ▁its ▁so fter