The average grade of the mineral of a vein type of orebody with grade and thickness varying from place to place within the same orebody is arrived by
Show Hint
For variable-width ore bodies,
\[
\boxed{
\text{Average Grade}
=
\frac{\sum(\text{Grade}\times\text{Weight})}
{\sum \text{Weight}}
}
\]
where the weight is usually thickness or tonnage.