The Gold Reserve for Australia is the gold held by a national central bank, intended as a store of value and as a guarantee to redeem promises to pay depositors, note holders (e.g. paper money), or trading peers, or to secure a currency. This value is in metric tons and includes the value of the gold in the current market based on a SPOT price of gold of $100.529 per gram.

However, there are varying estimates of the total amount of gold mined to date, mainly because gold has been mined for thousands of years around the world. Another reason is that some countries are not particularly open about how much gold they are mining. In addition, it is difficult to account for gold output in illegal mining activities.

References

The definition of Gold Reserves is from Wikipedia (https://en.wikipedia.org/wiki/Gold_reserve).