The unit precious metals are priced and reported in — 31.1035 grams, not the 28.35g of an avoirdupois ounce.
The standard unit of measurement for precious metals, equal to 31.1035 grams. Gold, silver, platinum, and palladium are typically quoted and traded in troy ounces. Not to be confused with the avoirdupois ounce (28.35 grams) used for everyday items.
Grades are reported in grams per tonne while output and reserves are reported in troy ounces, so converting between the two is routine. One gram per tonne over one million tonnes is roughly 32,150 ounces.