Snowden is the top company to deal with the nuggety effect.
It has produce a number of publication and some of these are Heterogeneity, sampling errors and the nugget effect in gold ores: implications for evaluation, exploitation and extraction
Dominy, S. C. and Platten, I. M. and Minnitt R. C. A. 2010. Heterogeneity, sampling errors and the nugget effect in gold ores: implications for evaluation, exploitation and extraction, in Proceedings of the Gravity Gold Conference, 3-17 (Australasian Institute of Mining and Metallurgy: Melbourne).
Approaches to reporting grade uncertainty in high-nugget gold veins
Dominy, S. C. and Edgar, W B, 2012. Approaches to reporting grade uncertainty in high-nugget gold veins, Transactions of the Institutions of Mining and Metallurgy (Section B: Applied Earth Sciences), 121(1), 29-42.
The results is that the
High-nugget effect vein-gold systems are generally considered to be one of the most challenging of deposit types to evaluate and exploit. To potential investors and mining companies, they are viewed as high risk because of the associated uncertainties in the grade estimate and general paucity of Ore Reserves at production start-up. However, despite the well-known risks, these deposits often have a grade upside that makes them potentially attractive. The reporting of resource grade is of importance and perhaps even more so is the reporting of the associated uncertainty attached to the grade estimate. The use of the grade estimate supported by a grade range is recommended to achieve more complete and useful disclosure. The definition of the grade range can be somewhat subjective, ranging from opinion based estimates through to data-based estimates and geostatistical conditional simulation. Whichever method used, the over-riding issue must be the provision of enough data of appropriate quality and full disclosure to the public of relevant uncertainties.