What is the meaning of the rotating base symbol?

[Sonoma]

My gnome alchemist has a rotating symbol at her feet. It is not there at login, appears after casting some spells. Stays on after completion of quest.

Sometimes it is 4-pointed, sometimes 3-pointed. What does it mean?

[Ilindith]

My gnome alchemist has a rotating symbol at her feet. It is not there at login, appears after casting some spells. Stays on after completion of quest.

Sometimes it is 4-pointed, sometimes 3-pointed. What does it mean?

Those are your reactions. They activate after you cast two spells of different color in a row. If you are currently in a reaction you will need to cast a color outside of the current reaction to swap to another.

Green (Verdanite) = Blue/Yellow

Orange (Pyrite) = Yellow/Red

Purple (Orchidium) = Red/Blue

They provide various bonuses bonuses while active. Green gives healing/neg spellpower, orange elemental spellpower and purple gives PRR.

They also provide a "spike" bonus for 12sec when they activate. Green gives DCs, orange reduces SP costs and purple gives elemental resists.

"Spikes" also boost the regular reaction bonuses even higher during those 12sec.

Enhancement trees also provide additional bonuses to the different reactions.

[GeoffWatson]

Go to your Feat list on your character sheet.

Under "Alchemist Feats" there's a feat called "Alchemist Spellcasting" which explains how that works.