U pb dating of zircon
Slow cooling means the individual mineral grains have a long time to grow, so they grow to a relatively large size.
Intrusive rocks have a characteristically coarse grain size.
Among the most common types of sedimentary rocks are sandstone (made from sand cemented together), limestone (made from the skeletons of lime-secreting plants and animals such as coral cemented together), shale (made from clay cemented together), and conglomerates (made from gravel cemented together).
The natural laws that create gems are the same as those that create snowflakes and salt, except that tremendous pressures and temperatures are needed.Diamonds can only form at depths of 100 miles or more below the earth's surface where pressures are a million pounds per square inch and temperatures are above 2,500̊F.╿ How do we get minerals?Minerals must be mined from the ground, either by surface, underground, or drilling methods.This process begins when water traveling through rock dissolves some of the minerals, carrying them away from their source.Eventually these minerals are redeposited when the water evaporates away or when the water becomes over- saturated.