Ann: High Grade Drill Results and Further Visible Gold, page-77

In these systems, if you are getting the quartz reef (vein) and bit of VG you are pretty happy, and have to take the "surprisingly high" assays with the "surprisingly low" - this is the effect of taking a thin core of rock through a nuggety gold system. In one high-grade vein field I worked on, the rule of thumb was that if one-in-three holes through the vein had an "ore grade" intercept (think >30 gram x metres), you could probably mine it. Normal fire assays should work fine, but people often do screen fires just to quantify how much coarse gold there is.

Seth, if those are the angles involved (didn't read that bit), you are probably on the money with true width. I was just having a stab from some low angles in the core photo (means the hole is sort of sliding along the vein somewhat).