Standard Assays and Sophisticated Assays
There are primarily two types of assays used to evaluate a project, standard and sophisticated. The standard assay determines how much free milling gold is in a sample, whereas a sophisticated assay will show how much total gold and precious metals are locked up in sample.
Standard Assay
Standard assays are used to establish how much free precious metals are in a mapped reserve that are recoverable by standard processing operations. Standard assays are appropriate if the gold in the sample has been liberated, is not masked by other elements, and the interfering elements have been taken care of and the gold is not subject to volatilization. All conditions must be right and met before a standard assay will properly evaluate an ore sample.
Sophisticated Assay
Sophisticated Assays are highly advanced assays that are designed to establish how much free, complex, and micron precious metals are in a mapped reserve, using any number of refined pretreatments before assaying a sample. These assays are used to determine the raw value of an ore sample without first doing an expensive metallurgical study to identify the needed pretreatment process. This is the main type of assay used in developing the Verbena Project. The assay analysis firm used seven special pretreatments to prepare the samples to be assayed by the Inductively Coupled Plasma method. Some of these pretreatments are toxic and cannot be used in a processing operation. With the use of these pretreatments a wide range of complex issues were resolved which allowed the assays to detect more of the gold and other PGMs within the Verbena ore body.
Assay Value of a Project
The assay value is used in a project evaluation process to establish how much wealth in the form of precious metals is located within a project’s mapped reserves. It is important to remember that these assays do not establish the extraction value of a project or its ore body. Instead, these assays provide an extraction target to strive for.
Extraction Value of a Project
While understanding the assay value of the reserves is important, the market value of the reserves is the project’s extraction value, not the assayed value. The extraction value is the value of precious metals that can be recovered from a mapped reserve with a production plant using affordable mechanical processes that are environmentally friendly.
There are thousands of pretreatment combinations that can be used. If gold is in the sample and the proper pretreatments have been performed, the assay will be accurate. However, it takes skill, and it takes a sample study before the proper pretreatment process can be identified. The exception occurs when standard assays are accurate without pretreatments which happens when the gold content of the sample is free gold, and the sample is not highly mineralized. For maximizing the results of an assay sampling, a sophisticated assay will be required.