From Sonic Retro
The Sol Emeralds (from Latin "sol", sun) were introduced in the DS game Sonic Rush. They are the Chaos Emeralds' equivalent in a parallel dimension; Blaze the Cat is their guardian. Each Sol Emerald shares the same color as its Chaos Emerald counterpart. The main distinction between the Emeralds, however, is that Chaos Emeralds carry the shape of a brilliant cut, whereas Sol Emeralds carry the shape of an emerald cut.
Their powers revolve around fire, hence their name. According to Eggman and Eggman Nega in Sonic Rush, both sets of Emeralds can be used to repel and attract each other, and when brought together, their power could be used to destroy the world. Although the Sol Emeralds seem to temporarily lose power, Blaze becomes capable of using their powers after Sonic gives a short speech about trust. From this, it is possible that the Sol Emeralds, much like the Chaos Emeralds in Sonic Adventure, are linked to their user's feelings and intentions.
In Sonic Rush, Blaze automatically collects the Sol Emeralds for every boss she defeats, rather than having to clear a Special Stage like Sonic does. However, in Sonic Rush Adventure, the player collects them by completing Blaze's side missions, unlocked at certain points of the game by speaking to Gardon the Koala. In both games, the player must gather every Sol and Chaos Emerald in order to access the Last Story level (Exception in Rush and Deep Core in Rush Adventure).
|Items in the Sonic the Hedgehog Game Series|
|Collectibles||Ring | Red Star Ring | Emblem | Chaos Drives | Material|
|Power-ups||Shield (Water, Lightning, Fire, Gold) | Invincibility | Power Sneakers | Combine Ring | Power Core | Light Cores|
|Level Objects||Monitor | Spring | Spikes | Checkpoint | Time Warp Plate | Signpost | Goal Ring | Giant Ring | Capsule | Button | Bumper | Speed Booster | Air bubbles | Chao container|
|Powerful Items||Chaos Emeralds | Super Emeralds | Master Emerald | Time Stones | Chaos Rings | Precioustone | Sol Emeralds | Jeweled Scepter | World Rings | Excalibur | Phantom Ruby|
|Weapons||Piko Piko Hammer | Chaos Energy Cannon | Caliburn | Wispon|
|Devices||Remote Robot | Combi Confiner | Mother Computer | Nega's Camera | Arks of the Cosmos | Miles Electric|
|Other||Chili Dog | Scepter of Darkness | Cacophonic Conch|