Sol Emerald

A set of Emeralds from another dimension, the Sol Emeralds appear in Sonic Rush and its sequel Sonic Rush Adventure, where they are guarded by Blaze the Cat. They are similar in function to the Chaos Emeralds, but they are rectangular in shape (emerald cut) unlike the pointed shape (brilliant cut) of the Chaos Emeralds. Like the Chaos Emeralds, all seven can be used to achieve a transformation (named Burning Blaze in Blaze's case). It is also interesting to note their magnetic properties - both Eggman and Eggman Nega quote that the Chaos and Sol Emeralds can attract and repel each other, and this power could destroy the world. There is currently no known Sol equivalent to the Master Emerald.

Name
"Sol" translates to "sun" in a variety of languages, and is the origin of the word "solar".

Theories
It was thought within the Sonic fanbase that the Sol Emeralds were to have a role in Sonic the Hedgehog after it was confirmed that Blaze would be returning in the game as an ally of Silver the Hedgehog. However, this turned out to be untrue as it was also revealed that this Blaze hailed from the future of Sonic's dimension, the full story behind the Sol Emeralds is unknown.

However it is thought that, because this Blaze's world was actually the future, it's possible that the Sol Emeralds due to them being able to allow characters to enter a Super Form and have the same attraction to eachother that the Chaos Emeralds have, are the Chaos Emeralds, having changed their look in the future for some reason. The Sol Emeralds could be of what's leftover of Solaris. However, it can be considered untrue.

One Fan's opinion is that Blaze may have moved into Sonic's Dimension in the distant future, and possibly travels between dimensions for many many years, while Solaris may possibly be the reason Blaze was in Sonic's dimension in the future because Solaris could be the Sol Emeralds' equivalant to Chaos

The canonicity of Sonic the Hedgehog is in question as the ending of the game shows that the events were retconned out of existence.