What specific background items drop loot?

Starting in 1.2, I've noticed that some background items in the world will drop loot. For example, occasionally you will find a small mound of dirt (usually a 2-wide by 1-high sprite) with a few gemstones of a certain color sticking out. Destroying this mound with your pickaxe will usually cause a random number of that type of gemstone to drop. I've also encountered similar sprites that, when destroyed, drop coins (usually either silver or gold coins).

Are there other world items that drop loot like this (ignoring pots, of course)? I've seen a mine cart once before, but it didn't seem to drop anything when I destroyed it. Are there rare background items that drop anything besides gems or coins?

Update: I finally managed to get a screenshot of one of these items. This particular item dropped 10 gold coins (!!!) when I destroyed it.

(Update: Added info on the Enchanted Sword, which I didn't know about)

Available background items (as of 1.2.4.1) include coin stashes, gem stashes, and the Enchanted Sword, the latter of which is surprisingly rare. Here are a couple of photos showing what the typical gem stash looks like:

As with most aspects of this game, the quantities for coin and gem stashes seem to be random, but they appear to be capped like this:

• Copper coins: up to 1000 coins
• Silver coins: up to 100 coins
• Gold coins: up to 10 coins
• Gems: up to 5 or 10 gems (depending on gem rarity, most likely)

Coin stashes only exist for copper, silver, and gold coins (there are no platinum stashes). Gem stashes exist for all gem types, even diamonds.