What are Troy Ounces?
A troy ounce is the unit gold, silver and platinum prices are quoted in. It is about 10% heavier than an avoirdupois ounce, but a troy pound has only 12 of them.
One troy ounce is equivalent to approximately 31.1035 grams, which is about 10% heavier than a standard avoirdupois ounce. The term "troy" originates from the city of Troyes in France, where this unit of measurement was historically used in the trade of precious metals.
What is an avoirdupois ounce?
An avoirdupois ounce is the ordinary ounce of the imperial and US customary systems, as opposed to the troy ounce used for gold and silver.
It is equal to 1/16 of a pound or approximately 28.35 grams. The avoirdupois system is based on a pound of 16 ounces, with larger units such as tons and pounds used for heavier measurements.