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Issue description:

Tools used: primarily obsidian paxel. Some slabs were also tested with an obsidian pickaxe, diamond pickaxe, or wooden pickaxe, with no change in results.
Slab varieties tested: All vanilla slabs, all Mekanism plastic slab varieties. All slabs were tested as single and double slabs.
Results, mining speed: All vanilla slabs except warped and crimson break almost instantly with obsidian tools. When Mekanism plastic slabs are mined with a pickaxe, paxel, or other mining tool of any unenchanted speed, their time to be broken is extremely long, nearly as long as an obsidian block mined with an unenchanted diamond pickaxe, and no faster than when broken by bare hand. This applies to both single and double slab forms of the blocks.
Results, drops: All single slabs drop 1 slab upon breaking. All vanilla double slabs drop 2 slabs. All standard Mekanism plastic double slabs drop 2 slabs. All glow and transparent plastic double slabs drop 1 slab.

Steps to reproduce:

1. Place all varieties of the game's slabs in the world in slab and double slab form, empty player inventory
2. Break slabs with a mining tool, noting the time taken for blocks to be broken.
3. Some double slabs will yield 2 slabs when broken, some will yield 1.

Version (make sure you are on the latest version before reporting):

Forge: 32.0.106
Mekanism: 10.0.8.431