Which objects give me elemental gems when I hit them?

So far, I've noticed in Chantelise that when I swipe at grass, I occasionally get a green elemental gem, and when I hit a tree, a yellow elemental gem drops out. What are all the objects like these that yield elemental gems when I attack them?

Solution 1:

You can get green gems by hitting tufts of grass. These are pretty much the most frequent and easiest to find, which is great because Air spells are awesome.

You can get yellow gems by hitting trees. Unlike grass which grows in caves, there aren't a lot of trees inside places, but there generally are multiple trees in any stage.

You can get blue gems by destroying barrels. Barrels, despite being, y'know, constructed things, can be found practically everywhere. Sometimes they may have food, but in general you're getting blue gems.

You can get red gems by destroying torches. You don't see these outside often, but you can find a lot of them indoors.