Cinderpearl is a type of plant found in deserts. They glow with an eternal flame, but the light they produce is not enough to prevent mobs spawning. They drop themselves when broken, and can be placed in a crafting table to get Blaze Powder.
They do not reproduce, and cannot be farmed.
Thaumonomicon Entry Edit
Found only in the hottest of climates, these plants burn with elemental fire. They can be harvested and ground to produce a fine powder akin to Blaze power.