BRICS is an acryonym. it is not a type of economy. It is not a trading bloc. It doesn't have a currency.
BRICS stands for Brazil, Russia, India, China, and South Africa.
That said, Russia and China are in the process of issuing a gold backed currency. This is a block chain currency that is redeemable in gold, and is limited by the amount of 'gold on hand'. In other words, it's paper gold. It remains to be seen whether this will actually work. Oh...and Texas is thinking of issuing one too (it's legal for Texas to do so...indeed, it's legal for any State to do so).
The dollar has no backing at all. It is not redeemable for gold or any other commodity. It has no inherent value at all.
If the federal government were to use all of it's gold to pay off the national debt, it could pay off only about 5% of it. In other words, the federal government is broke.