Traumatic optic neuropathy (TON) refers to an acute injury of the optic nerve secondary to trauma. The optic nerve axons may be damaged either directly or indirectly and the visual loss may be partial or complete.
In Minecraft, emerald ore is very hard to find and is found in small deposits in the Extreme Hills biome. You can usually find emerald ore between 13 and 31 blocks below the ground and close to lava. So if you see a pool of lava in the Extreme Hills biome, that is a great place to start mining downward.
Ruby was originally planned to be added as part of Minecraft patch 1.3, but was abandoned in favor of Emerald by developers. Variations of Armor and tools crafted with ruby were another idea which could have been incorporated into the update, but those plans were obviously also abandoned when rubies themselves were removed.