OREAS 235b was prepared from a blend of high-grade, gold-bearing ore and barren metasediments. The ore was sourced from the Fosterville Mine, located 20km from the city of Bendigo in the state of Victoria, Australia. The deposit is hosted by a metamorphosed interbedded turbidite sequence of sandstones, siltstones and shales. Primary gold mineralization occurs as disseminated arsenopyrite and pyrite in a quartz–carbonate veinlet stockwork. Primary gold also occurs as visible gold where it variably overprints sulphide mineralization and is found as disseminated fine specks (>1 mm) of gold within host quartz veins. The visible gold is spatially associated with antimony mineralization, in the form of stibnite that occurs with quartz and varies from replacement and infill of earlier quartz-carbonate stockwork veins, to massive stibnite-only veins of up to 0.5m in width (Hitchman, Philips, & Greenberger, 2017). Thirty-five commercial analytical laboratories participated in the program to certify the elements shown below. The following methods were employed:
- Gold by fire assay
- Gold by aqua regia digestion (15-50g sample weight)
- Gold by cyanide leach
- Gold by X-ray PhotonAssayFull ICP-OES and ICP-MS elemental suites by 4-acid (HNO3-HF-HClO4-HCl) digestion
- Full ICP-OES and ICP-MS elemental suites by aqua regia digestion
- Instrumental neutron activation analysis of Au on 20 x 85mg subsamples to confirm homogeneity (undertaken at ANSTO)
| |
Analyte
|
Certified Value
|
1SD
|
CRM State
|
Matrix
|
Mineralisation
|
| |
Au by fire assay
|
1.63 g/t
|
0.053
|
primary
|
metasediments
|
orogenic lode gold
|