Glowstone

Glowstone is a useful light source as it provides a wide area of light for no power.

Obtaining
To obtain glowstone, go to the Blazing Fortress. Once there, go to the Pigman area and keep going straight from it. Eventually you'll find glowstone. Unless you have a silk touch tool, glowstone will drop into small amounts of glowstone dust. You can also obtain glowstone dust, enchanted glowstone dust, and enchanted glowstone blocks from the Bazaar.

However, the amount of glowstone dust is almost always enough to craft a block of glowstone. Unlike most other blocks, glowstone can be crafted with only four items instead of nine, similarly to a quartz block.