37 PRODUCTS N at ur a l r en ew a b l e a n d gl o b al l y a va i la b l e Nearly 4 of the earth s crust is composed of Calcium Carbonate making it one of the most common raw materials in natur e It is continuously r eplenished by natural cycles in rivers lakes and oceans or formed as minerals for example as shells or skeletons Calcium Carbonate in the form of marble limestone or chalk is a natural and r enewable material as defned by ISO 14021 for its r eplenishment rate much gr eater than its rate of use 1 Commer cial grades of Calcium Carbonate ar e mainly pr oduced r egionally or locally due to sour ces being widely available ar ound the world 1 S o u r c e C a l c i u m C a r b o n a t e A s s o c i a t i o n Eu r o p e M e m b e r o f I M A Eu r o p e