Still, maybe, they should rather be called “mega-nuggets.”Īdding to the extreme rarity of discovering such silver boulders is the fact that silver disintegrates and falls apart naturally, so even if huge boulders were once formed, over the millennia, they have been broken down by nature’s forces.Īt the TGMS show, I talked to Dr. So, compared to the largest surviving gold nugget, the silver nuggets recently discovered are two to three times larger, and fall into the boulder-sized category. In comparison, the world’s largest surviving gold nugget is the Pepita Canaã (Canaan Nugget), mined in Brazil in 1983, which has a gross weight of 60.82 kilos (134.10 pounds) and contains 52.33 kilos of gold, or 1,682 troy ounces of gold. We are more familiar with gold nuggets, which range from a few grams to huge native gold specimens. The term nugget may be more appropriate, defined as a solid, native lump of precious metal. Boulders are often smooth rounded masses of rock with a diameter greater than 25cm that have been shaped by erosion and transported by ice or water from their original position. We normally call boulders large rocks without huge monetary value. I am not sure that the term boulder truly reflects the rarity of these specimens. But what I found even more intriguing was the astonishing story of the rarity of the discovery. Their dark appearance is due to a natural coating of cerargyrite (AgCl - silver chloride). Despite being dark and not flashy, they were truly imposing specimens.
I was taken by their spectacular size and the mesmerizing textures on the surface of the boulders. I must confess, while there were fabulous mineral specimens of gold, tourmaline crystal clusters, and more, these silver boulders truly stood out for me. I am so glad I had the opportunity one morning before opening our booth to take a quick walk around the exhibits. The trio of spectacular silver boulders was on exhibit at the 2020 Tucson Gem & Mineral Show® (TGMS). They have not been waterworn or rounded, as they have not traveled down a river. These boulders were found near each other in an arroyo (or stream bed), where they had traveled only a short distance after becoming dislodged by weathering from their vein outcrops. The largest silver boulder weighed 417 pounds when it was unearthed, and now, after cleaning, tops 411 pounds. These enormous natural specimens of precious silver weigh 610 pounds collectively, or 8,896 troy ounces. Three huge silver boulders and an assortment of smaller specimens were discovered near Globe, Gila County, Arizona, during a careful search that lasted about two years. An exhilarating new find made in 2018 that represents the largest surviving group of native silver nuggets in the world continues to generate global interest and excitement.
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