"The presence or absence of very high-value stones can have a huge impact on the overall valuation.” While that doesn’t mean one stone can make or break a valuation, Armstrong noted that “one stone can make a huge difference.” The main reason is that “if you see [a large stone], then you know they exist — you can argue then about … how frequently they might realistically appear in a production scenario.” However, if such stones don’t turn up “it’s a lot tougher, you’re trying to prove a negative in a sense.”
