In radioactive materials a parent atom decays into a daughter, such as uranium-238 decaying into lead-206. For some radioisotope
dating methods you have to assume you know the amount of daughter atoms in the crystal, so you can tell how much is a result of radioactive decay (and thus get an age for the rock). Please answer this question: why are zircon crystals so useful for uranium/lead dating? If you don't remember from class, can you read this article.
In order for scientists to know how old a fossil is they use the process of fossil dating of relative dating. The most common method of dating is the Uranium-lead dating. There are multiple minerals used for uranium-lead dating, the most common/preferred is Zircon. The mineral zircon is ideal because:
Zircon is a hard mineral, this makes it impervious to weathering.
It is resistant to chemical and mechanical weathering, and metamorphism
We know the formula of the density: ρ = ; So the mass will be equal to: m = ρ * V = 2.70 * 21.3 = 57,51 g = 57510 mg of substance. So the answer is 57510.
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