N a tu r a l 80 94 C Se d i m e nt a r y T y p e S y nt he ti c 9 9 C 1 5 Mt yr 7 0 00 2 00 00 t Hy d r o t h e r m a l V ei n h ig h es t pri c e h ig h purity crystallin ity 16 So u rce US G eolog i c al S u r v ey I n d u stria l M i n era l s R oski l l N at ur al 9 9 C V ol c anic T ype Z e n y a tt a GRAP H ITE 10 Mt yr F l a k e m ed ium pr i ce 5 00 1 5 0 0t A m orphous lowe s t price 3 00 5 0 0 t