woods point geology, page-53

Hi all,

I will post this rather technical reference on sampling and assaying for anyone interested. The reference is specific to the nuggety ground in Vic goldfields but it has wider application as well.

http://www.iom3.org/divisions/earth_sciences/mre21/dominy.htm

For those who prefer a 30 second shortcut, here's a quick tour of types of assays.

TFA Traditional fire assay takes a 100g sample. The gold is extracted and weighed.

SFA Screened fire assay takes a 1kg sample. Crush the sample to a nominal 75 micron. Being malleable, the coarse gold will flatten rather than crush and can be screened off and fire assayed separately. A 100g sample of the tailings is fire assayed as well. Results can be reported separately or combined as a total assay.

BLEG Can't remember the acronym but a several kg sample is leached with cyanide and the gold is extracted from the solution.

For nuggety ground, a bigger sample means greater accuracy provided sampling errors have been avoided. This is why bulk samples are needed to be sure of grades.