Parabolic Behavior at the Origin

This very regular behavior at the origin is seldom found in mining practice. In the absence of nugget effect, it corresponds to a random function $Z({/boma x})$, which is very continuous in its spatial variability. Thickness variograms of continuous sedimentary beds sometimes display such a parabolic behavior at the origin, but are usually accompanied by a slight nugget effect due to errors of measurement.

(c)

Gaussian model:

The sill is reached asymptotically and a practical range can be considered with $a'=/sqrt{3} a$, for which $/gamma(a')=C(1 - e^{-3})=.95C$, cf. Figure 4.15.