Railcraft materials in RFTools dimlets show as unknown dimlet
These ones:

milte.railcraft.brick.nether2
milte.railcraft.brick.bloodstained2
milte.railcraft.brick.infernal2
milte.railcraft.brick.infernal5
milte.railcraft.brick.abyssal2
milte.railcraft.brick.sandy2
milte.railcraft.brick.quarried2
milte.railcraft.brick.frostbound2

Example screenshot: http://i.imgur.com/rIxfXsU.png

I dont know if this is Railcraft issue or RFTools issue, but I also opened an issue at RFTools:
McJtyMods/RFTools#299

Modpack Direwolf20 1.7
Railcraft_1.7.10-9.6.1.0
mcjtylib-1.2.0

I have both RFTools and Railcraft. The "is missing!" message indicates that dimlets for those blocks previously existed but no longer exist. Perhaps they were added by config and the config was subsequently wiped out?

Dimlet??

Dimlet, think rf powered mystcraft.

Most likey NOT a railcraft issue.