Cragwood Leaves grow on chestnutbrown-barked Cragwood-trees with Yellow Flowers in Grassland, Woodlands and especially Forests.
Blocks of leaves can be harvested/pulled with your arctek-gauntlet without needing any Power Cells. If you use Stone Mining Cells or better to pull leaves, these stronger Power Cells will not even lose durability.
In Creativerse leaves will not decay / vanish by themselves when you "cut" down the stem of the tree nor if you take away all the wood-blocks that the tree is made of. Instead the blocks of leaves (as well as all Flower-blocks, Beeswax, Vines, etc.) will prevail and float in the air until you take them down manually or use Excavators on them to collect at least half of them.
You can of course also throw Explosives at leaves and/or burn them. As leaves are inflammable, burning them might work overly well in warm environments. So beware of forest fires that will also burn down all the wood and Tallgrass! On the other hand burning attempts might stay below expectations in cold environments. Simple torches cannot even set fresh leaves aflame in snowy biomes (as of R25 in November 2015).
One block of Cragwood Leaves can be made into 4 blocks of Shredded Leaves in the Processor. Taking/crafting Shredded Leaves will unlock the recipe for three types of colored carpets. Shredded Leaves burn even easierly than fresh leaves when being placed (even on snow) and can be used as a fuse for Explosives very well.
Cragwood Leaves can be placed as solid blocks for decoration and can also be used for building; however they can make creatures spawn, like Leafies during the day, and Night Leafies in darkness.
Cragwood Leaves can be used as Fuel for the Forge, however 4 blocks of leaves are needed and used up for each melting-/hardening-process. Also each melting-/hardening process in the forge will take quite long when you use leaves as fuel.
Cragwood Leaves can be corrupted into Corrupted Leaves, for example by using Corrupt Bombs on them. By that they will turn into better fuel, but they have to be picked up using Lumite Mining Cells, which will reduce the durability of the Mining Cells quite a bit (just like pulling all other kinds of corrupted blocks).
You can lay out Cragwood Leaves to make Yellow Flowers grow on them, but that will take quite some time (a few RL-days for each new block of yellow flower). You can also plant Queen Bees on Cragwood Leaves to grow Beeswax, which will take ca. 3,5 hours (real-life time). You can grow whole Cragwood-trees from Saplings too. If you place 4 Saplings together, larger trees will grow. Grassland is not a good biome for them though, so Cragwood-Saplings might stay fallow there.