Nether Quartz Ore is a material block added by vanilla Minecraft. It is the only Nether ore that has been introduced in Vanilla thus far. Nether Quartz ore can generate at any elevation and is very fragile; even a Wooden Pickaxe can mine it and still yield drops. They seem to drop more mining XP than other ores.
When mined, Nether Quartz Ore drops one unit of Nether Quartz, possibly more if your pick is enchanted with Fortune. A pickaxe with Silk Touch harvests the actual ore block, which can be smelted in a Furnace for one Nether Quartz.