OREAS 270

OREAS 270 is a low-level gold certified reference material produced from a
blend of barren mudstone–hornfels units and finely disseminated low-grade
Blackwood gold mineralisation sourced from central Victoria, Australia. 
These materials provide a robust, well-behaved matrix suitable for quality
control of low-level gold determinations.
The dominant component of the matrix is barren Mansfield hornfels, a
fine-grained, metamorphosed mudstone–siltstone unit representative of Victorian
sediment-hosted sequences. The barren backbone is complemented by scoria and two
distinct Blackwood mineralised units.
OREAS 270 has been characterized using the following methods:

Gold by Pb collection fire assay (25-50g charge weight) with AAS and
ICP-OES finish
Gold by Bi collection fire assay (30 g charge weight) with AAS finish
Gold by 15-50g aqua regia digestion with ICP-MS and AAS finish
Gold by Bulk Leach Extractable Gold (BLEG) with low-level instrumental
finish
Full 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
Certified values for applicable analytes are operationally defined for each
method, with results under OREAS ISO 17034 scope of
accreditation.