How can variations in gravity be used to estimate the amount of ore?

Question

Describe how careful measurments of the variation in gravity in the vicinity of an ore deposit might be used to estimate the amount of ore present?

Answer 1

The equation
g = G*m/r^2
assumes uniform distribution of density. To be rigorous you need to consider each spec making up the earth and how far it is from the point you're calculating the gravity for. Then sum the affect of each spec to get total gravity.

The magnitude of local gravity is affected by deposits close to the surface of more dense (or less dense) material than normal. Geologists can probably make a good guess at what's in the deposit.