When Dr Gey realized he had an immortal line of human cells, he sent samples all over the world. Soon the world's first cell production facility was churning out
Hela cells per week."

You have been tasked with sorting the rock samples shown into three categories, with two rocks in each category. what attribute would you use to sort these rocks? which rocks would be in each category? rocks: obsidian, coquina limestone, granite, soapstone,pumice, and gneiss.