Pumice and obsidian are both forms of volcanic glass. What are one similarity and one difference in the composition of these two rocks?
1) Both rocks are composed largely of silica, but pumice is light in color and can float on water, while obsidian is dark due to dark-colored minerals distributed within.
2) Both rocks are composed largely of silica, but pumice is dark due to dark-colored minerals distributed within, while obsidian is light in color and can float on water.
3) Both rocks are composed largely of silica, but pumice is commonly used to make jewelry and surgical instruments, while obsidian is commonly used in soaps and cleansers, concrete and plaster.
4) Both rocks are composed largely of silica, but pumice is commonly used in soaps and cleansers, concrete and plaster, while obsidian is commonly used to make jewelry and surgical instruments.
