You may recall that we (the mere taxpayers) were told that the Amerithrax spores had been weaponized with silicon. Then, later, we were told: No, no... there was only a trace amount of silicon and had not been weaponized.
According to Edward Jay Epstein in the Wall Street Journal, this "trace" amount was 1.4%—i.e., more than what microbiologists would consider "trace." He says that researchers at the LLNL have been unable to replicate accidental contamination with silicon that is anywhere close to 1.4%.

H/T Kevin McElroy