Although this article is based on official information, the actual name of the article's subject is pure conjecture.
Emerald Blocks are gimmicks that appear in the Sonic the Hedgehog series. They normally float in the air and act as platforms, but also harbor additional properties when stood on, depending on the time zone.
As the name implies, Emerald Blocks are platforms shaped like the titular gemstone. The color varies based on the timezone the player is currently in; they are orange in the Present, brown in the Past, purple in the Bad Future, and golden in the Good Future.
In Sonic the Hedgehog CD, Emerald Blocks make their first and only appearance in Palmtree Panic. They are always found floating in the air, though some are placed in rows to connect two platforms to one another. Unlike most other objects in the game, Emerald Blocks are always found in the exact same locations in every time zone, even if the level layout around them changes. Also of note is that depending on the time period the player is in, the Emerald Blocks will act differently when stood on:
Present: The Emerald Blocks are completely invisible, only revealing themselves when stood on by the player. When the player steps off of them, they will phase out of existence again.
Past: In the Past, all Emerald Blocks are completely visible and can be stood on as long as the player wishes.
Future: In both the Good and Bad Futures, Emerald Blocks are visible like in the Past, but will slowly sink downwards once the player steps on them, and will continue doing so even if the player steps off.