The recent increase in demand for lithium has lead to the development of new brine prospects, particularly in the central Andes. The brines are hosted in closed basin aquifers of two types: mature, halite dominant, and immature, clastic dominant. The estimation of elemental resources in these salars depends on a detailed knowledge of aquifer geometry, porosity and brine grade.The geometry of the aquifers can be evaluated by classical geophysical and drilling techniques, but since the resource is a fluid, with the attendant problems of in-aquifer mixing and dilution, existing codes for filing resource and reserve estimates need modification. Total porosity is 2 relatively straightforward to measure, but effective porosity and specific yield, which are required to estimate the resource, are rather more difficult. Recovery factors are low compared with metalliferous and industrial mineral deposits due to reliance on pumping for extraction.These and related issues are discussed in-depth, and suggestions for changes to the reporting of resources and reserves are put forward for such brine prospects.

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