Yes, you read it right. I'm not really adding this for the sake of realism, but for the sake of a rather useless biome. Gold ores will generate at levels 1-62/63 since stone generates at levels 53-58.
Gold ores would not generate at riverbeds. But, a new kind of block will. This is basically a gravel with a few textures of gold. When shoveled, will drop 2-3 pieces of gold nuggets and a normal gravel or flint. It will drop the normal gravel, not the 'gold gravel'. Like the normal gravel, it will be affected by gravity. It will be a bit longer to break than normal gravel.
'Gold gravel' is not guaranteed to spawn in veins under the riverbed. Normal gravel, dirt and will spawn more often than gold gravel under the riverbed. And, gold gravel and normal gravel are very hard to distinguish with each other because of the very small differences. So if you want to get gold nuggets under the riverbed, shovel every gravel you see. There would be approximately 6-10 blocks of gold gravel that will spawn on the riverbed at every river.
The Gold ores under the river biome will spawn in 4-8 blocks (like normal gold ore generation) ON EVERY VAIN. Gold gravel WILL NOT spawn in other biomes naturally except in riverbeds.
Considering that river biomes are going to be a gold farm for players, river biomes will now be 1.5x rarer. (CrazyChippy's suggestion)
When you use a Fortune shovel on a 'gold gravel':
For the gold gravel, level I gives a 33% chance to multiply the nuggets by 2 (averaging 33% increase), level II gives a chance to multiply the nuggets by 2 or 3 (25% chance each, averaging 75% increase), and level III gives a chance to multiply the nuggets by 2, 3, or 4 (20% chance each, averaging 120% increase). Same as when you use a Fortune pickaxe on a gold ore.
As always, I'm open to suggestions (postive or negative), discussions and criticisms. Also looking for textures who can make the gold gravel texture.