▁minutes , ▁may ▁only ▁be ▁present ▁in ▁the ▁labor ator ies ▁where ▁it ▁was ▁produced . ▁ ▁Group ▁ 1 2 ▁met als ▁are ▁ch al c oph iles , ▁meaning ▁the ▁elements ▁have ▁low ▁aff in ities ▁for ▁ox ides ▁and ▁prefer ▁to ▁bond ▁with ▁sul f ides . ▁Chal c oph iles ▁formed ▁as ▁the ▁cr ust ▁solid ified ▁under ▁the ▁reducing ▁conditions ▁of ▁the ▁early ▁Earth ' s ▁atmosphere . ▁The ▁commer cially ▁most ▁important ▁min er als ▁of ▁group ▁ 1 2 ▁elements ▁are ▁sul f ide ▁min er als . ▁S phal er ite , ▁which ▁is ▁a ▁form ▁of ▁z inc ▁sul f ide , ▁is ▁the ▁most ▁heavily ▁m ined ▁z inc - cont aining ▁ore ▁because ▁its ▁concent rate ▁contains ▁ 6 0 – 6 2 % ▁z inc . ▁No ▁significant ▁depos its ▁of ▁cad m ium - cont aining ▁or es ▁are ▁known . ▁Green ock ite ▁( C d S ), ▁the ▁only ▁cad m ium ▁min eral ▁of ▁importance , ▁is ▁nearly ▁always ▁associated ▁with ▁s phal er ite ▁( Z n S ). ▁This ▁association ▁is ▁caused ▁by ▁the ▁ge och em ical ▁similarity ▁between ▁z inc ▁and ▁cad m ium ▁which ▁makes ▁ge ological ▁separation ▁unlikely . ▁As ▁a ▁consequence , ▁cad m ium ▁is ▁produced ▁mainly ▁as ▁a ▁by product ▁from ▁min ing , ▁sm el ting , ▁and ▁ref ining ▁sul f id ic ▁or es ▁of ▁z inc , ▁and , ▁to ▁a ▁less er ▁degree