# Dictionary:Borehole gravimeter

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A remote reading gravimeter that can be lowered through a borehole as a logging tool. The difference between the gravity readings at two different depths gives the apparent density ${\displaystyle \rho (in\ {\frac {g}{cm^{3}}})}$ between the depths:

${\displaystyle \rho =3.686-{\frac {128.5\Delta g}{\Delta h_{1}}}=3.686-{\frac {39.18\Delta g}{\Delta h_{2}}}}$,

where ${\displaystyle \Delta g}$ is the gravity difference in mGal, ${\displaystyle \Delta h_{1}}$ is the depth difference in meters, and ${\displaystyle \Delta h_{2}}$ is the depth difference in feet.[1]

## References

1. LaFehr, T. R., 1983, Rock density from borehole gravity surveys: Geophysics, 48, 341–356.