Peppermint it ain't ;) Spearmint either...

It's one of the sweet mint cultivars.... Taste test it to see which one. All the flavored ones look nearly identical and there are a lot of them. My chocolate mint looks just like your plant. Plain sweet mint, too. So, yeah, go ahead and taste test one of the older leaves =) It's really the only way you're going to be able to confirm ID.

Actually, my younger brother did do that to see if he could tell what it was when I was asking him if he recognized it. He just said it tasted nasty! But I've generally found that it's difficult to tell the actual taste of the herb by the leaf itself. They all tend to taste the same to me that way. I can really only tell after making an extract or concentrate from them. But thank you for the suggestion!

People's tastebuds vary.... My mom can give you every single ingredient in a complex meal by taste alone, while my dad can't tell if he's eating chicken or pork chops.... LOL ... Try making tea from it (once it gets bigger) -- sometimes the hot water brings out the flavor hidden in the plant (chocolate mint is like that). The more mature the leaf, the more flavor it will have, too... And the oils are even more concentrated in the stems of most mints.

The upside is that virtually all mints make good tea ;) So you can't go wrong there. And if your tastebuds can't pick up the subtle flavor, heck, go ahead and use it for whatever ;) The stuff's good for ya regardless ;)

Good luck with further ID...

Just now I was studying pictures of different varieties of mint plants and I have to say I am almost convinced that what I have is a Chocolate mint plant after studying a few pictures of said plants.