Where does “green sand” come from?

green sand (English) comes from English green, from Middle English grene, from Old English grēne, from Proto-West Germanic grōnī, from Proto-Germanic grōniz, from Proto-Indo-European ǵʰreh₁- — to become green, grow; to grow; to green, to grow.

green sand (English): An aggregate of sand, bentonite clay, pulverized...