Precious-Metals Testing Methods

There is no single testing method that answers every question about gold. An ore sample presents a different analytical problem from a doré bar. A finished bullion bar requires a different approach again. The condition of the material, the way it has been sampled, the information the client needs and whether the material can be altered all influence the method we use.

At Bilex Minerals EA, testing is carried out in house using analytical and physical verification methods selected for the material and the decision the result needs to support.

XRF provides rapid elemental information without consuming the item during measurement. Bilex uses both handheld and desktop XRF systems. Suitable metallic surfaces are cleaned and polished where required, and more than one area can be measured when the purpose is to compare composition across the item. XRF is a surface region technique, so the result is interpreted with the condition and preparation of the measured area in mind.

Coarse gold distribution can make small analytical portions less representative. PhotonAssay measures a comparatively large prepared geological sample using high energy X rays and gamma detection while leaving the prepared sample intact. Metallic Screen Fire Assay uses a larger prepared mass, separates coarse and fine fractions, assays them separately and combines the results by their recorded weights. These methods answer different questions and are selected according to the sample.

Clients are not expected to select an analytical method in advance. The material form, approximate quantity, testing objective and whether destructive sampling is permitted are sufficient for our team to recommend an appropriate analytical scope.