The Nugget Effect. What is it, and how to recognize it. – by Andrew Watson (Geology For Investors – July 2018)

Andrew Watson is the principal of Anterrra Consulting, which provides strategic advice, project generation, investor relations services and digital data management services to clients in Mining, Junior Exploration and Oil and Gas.

One of the first things to recognize in the mining industry, is that all that glitters may not be gold. I’m not talking about the time the CEO of a junior exploration company picked up drill core freshly drilled from the corebox and called a zone of pyrite the best core he’d ever seen (it was if you like shiny things).

No, this is nature playing tricks on us. The core will assay 44 kilos of gold per tonne in 1 metre and 0.1 g/t per tonne the next. What’s even more frustrating, from the authors own personal experience, is when core is first assayed by one technique and then re-assayed by another and the gold disappears.

What happened? Did the assayer pocket that 5 grams of gold? Nope. There was a gold nugget, it was assayed the first time, and now it’s gone for the second assay. Welcome to the Nugget Effect. The Nugget Effect simply is the product of the clustering of metals in a given deposit.

Where metals are very tightly clustered (nuggety), then finding the nugget will give a wild overestimation of the amount of metal, inversely missing it will underestimate the amount of metal. Gold, and PGE’s are particularly susceptible to this as they are not reactive and are not commonly found combined with ore forming minerals.

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