mining question

Got my miner up to level ten, and I notice in the mining in interface, where it llists the available deposits, it says, for example,
Copper ore -
100% (chance of gathering), then below that there's a symbol with the number 15% next to it. What is that 15% and the symbol next to it? I assume it means I have a 15% chance of gathering a special kind of copper ore? What's so special, about it?

That symbol and percentage represent your odds of getting an hq ore. Hq, or high quality ores sell for more, because it's easier for crafters to make HQ items when they use HQ materials.

High quality. It sells for more gils, and you can use it for crafting high-quality products easier.

Ah, thanks.