No. It's all stemming from Mansa Musa handing out tons of gold when he made his pilgrimage to Mecca. It basically was a reverse gold rush. So, it put Mali on the map, and people assumed he had cities of gold.
Proof no. When I was down visiting a mayan ruin our guide told us the latest theory is that the temples had Black Obsidian on their exteriors. When sunlight hits it it appears gold in color. Remove it from direct sunlight it looks black. The conquistadors would see the gold in daylight from their ships, but when they tries to steal it at night they couldn't find it.
I bought a mayan statue made out Black Obsidian. It does shine gold in the sunlight, and is black while inside.