All you folks - and I include myself in that - who criticized XyCraft for the rendering lag caused by quartz: how surprising is it when I say that AE Quartz has exactly the same problem? That's right - Certus Quartz does not count as a solid block for rendering purposes. All 6 adjacent blocks are loaded into the rendering engine, and if you use an X-ray hack such as the redstone block fence trick, you can see all AE quartz rendered as though it were an air block.