" A Nether Quartz Ore is an ore only available in the Nether and is the only ore currently located there.
When mined with any pickaxe, it drops a Nether Quartz crystal, which can be used to make a Comparator, Daylight Sensor or a Block of Quartz. Like Coal, Redstone, Diamond, Emerald and Lapis Lazuli Ore, Nether Quartz Ore drops experience when mined, and works with both Fortune and Silk Touch enchantments.
Nether Quartz may seem to be very common, but is actually about as abundant as iron in the overworld. It simply appears to be more abundant because you can see more exposed surface area compared to caves in the overworld. This makes it a very easy task to find the ore. It is also available at any layer. There is an average of roughly 70 ores per chunk. "
So yeah... From MC Wiki