Crystal

Crystal is an ore added in with Version 1.1. It is currently the strongest and rarest ore in Ores Extended. It is used to create the current best toolset in the game, the Crystal Toolset.

Spawn Rate
It is the rarest ore in the mod, spawning at the same layers as Diamond but much more rarely. It spawns in blocks of 1 or 2.

Trivia

 * Crystal was originally named Runite before the Version 1.1 Fix Patch.
 * Crystal was originally even rarer then it currently is, spawning in approximately the last 4 layers before bedrock.