They are similar in size and shape to the large oak trees of vanilla, if not perhaps a little taller. They have distinctive blue leaves that sparkle, and the tree emits 7 levels of light, the same as a Redstone Torch.
Silverwood Logs take about 25% longer to cut than Oak Logs. You cannot craft Silverwood Logs into planks like normal logs, however you can create silver wood planks using a carpenter. You can still burn them for fuel or smelt them in a furnace to produce charcoal the same way as other logs.
Silverwood Logs and leaves are valuable as they are the only non-diamond source of the Purus aspect other than refined iron.
[Unless additional mods are added: e.g. IC2 Refined Iron has the Pure aspect too]
Destroying Silverwood leaves has a small chance of producing a Silverwood sapling. Those saplings can grow into a new tree, even in a 1x1 one block deep hole, provided that there is at least 100 vis in the area. To instantly grow a sapling, a Hoe Of Growth must be used; bonemeal does nothing when used on the sapling.
They will spawn a new pure Node in their second trunk block with about 50-100 Aura as base size and no Flux. If two or more trees grow about 8 blocks apart, their Aura nodes will fuse and move to the middle, resulting in higher capacity but also in Overcharge, which creates Flux.
Heres a video that shows you how silverwood works http://www.youtube.com/watch?v=qhK4fDhxuYo