How is the density of a substance calculated?

Which set of characteristics best describes igneous rock? a) largest type of rock, made of organic matter, hardest type of rock b) least abundant type of rock, made of other rocks, made mostly of minerals c) found on all continents, contains wavy bands of stripes, contains fossils d) most abundant type in earth's crust, made of magma/lava, contains no fossils

In 2002, the rare earth elements mine in mountain pass, california was closed because

What type of organic molecule comprises the majority of a potato?