Nether Quartz

Nether Quartz is a Nether exclusive item obtained by mining Nether Quartz Ore. This item had been added in snapshot and was released in the Redstone Update. Nether quartz are the essential ingredients to create redstone comparators, daylight sensors, and the Block of Quartz. They have already been released in the Pocket Edition.

Smelting
Note that the nether quartz ore block cannot be obtained without the Silk Touch enchantment, and that this smelting is slightly inefficient because with Fortune, you can get more than one quartz per ore. Also, there would be no reason to collect it with silk touch if you were just going to smelt it.

Trivia

 * Nether Quartz appears to be quite common in The Nether, but in reality, is about as common as Iron Ore in the overworld, each spawning approximately 70 ores per chunk. What makes it seem more common is that it can spawn on any layer within The Nether, combined with the fact that the Nether has more exposed blocks than an overworld cave, and the fact Netherrack can be removed far more quickly than Stone.
 * Nether Quartz can be obtained in Pocket Edition (current 0.6.1) when it is spawned by a Nether Reactor. Its only use is to craft Smooth Quartz block.