What can scientists learn from the rate at which radioactive elements decay?

a) the difference between molds and casts

b) the relative age of rock layers

c) a rock’s actual, or absolute, age

d) where one soil horizon ends and the next begins
! meh!

Pegmatites are igneous rocks in which the individual minerals are very large. typically, the minerals are all light-colored quartz, feldspar and muscovite. if you were given a black and white photograph of a pegmatite in a quarry (where the rock has been blasted and broken), what physical properties could you use to identify those three minerals in this hypothetical photo? describe each mineral and the specific diagnostic properties. be specific.