It is important to verify the companies' claims through other sources of information and not rely solely on the press releases. These elements are extremely rare and are not present in Nevada in commercial quantities. Fire assays, if properly done by a competent assayer, will produce accurate values for gold and silver. The only exception is if the precious metals are associated with tellurium. In that case Atomic Absorption analysis will be able to identify the gold and silver, as well as tellurium.
Gold tellurides are rare in Nevada.
Colorado has several telluride occurrences that have been mined in more recent years. While it is true that new techniques have been and are being developed to enhance recovery, secret recovery processes generally don't recover much, if they are valid processes at all. Usually hundreds of drill holes are required, with thousands of assays before reserves of this magnitude can be stated with any degree of confidence. Actual drilling is ongoing but is slow with one or two drill rigs. If a major new ore deposit is suspected by a legitimate company, there is significant incentive to get the drilling done as soon as possible so mine permitting and actual mining can begin.