A Rocky Friendship: Chet's Rock Collection

Even though I'm in Pakistan with Rida right now, I'm still trying to keep up with all the things you're learning. I heard you were learning how to classify (sort) rocks based on their properties or characteristics. You guys sure are learning a lot of new science words. It's hard for me to keep them all straight. I had Miss P and Miss Hoffmann send me a list of the new vocab words you've been using to discuss rocks and I'm a little overwhelmed.
I have a bunch of pet rocks in my collection, and I'm working hard to classify all the rocks I see according to the following properties: color, texture (ex. rough, smooth, bumpy), luster (shiny, dull, metallic, glassy), density (heavy or light), hardness (how solid is it...do small pieces crumble off on your hands...what would it take to scratch your mineral), and streak (by rubbing your rock across an unglazed piece of tile, does it leave a streak mark...what color is the streak). I am having a lot of fun sorting the rocks based on one or more properties at a time. It's just like "Guess My Rule," from Math Workshop.
I also heard that you learned about the three types of rocks: Igneous, Sedimentary, and Metamorphic. I have a favorite rock over here. It's very small, but it has different shades of brown in it. It looks kind of like the inside of a candy bar. A dark layer, then two lighter layers, and another dark layer. When I'm really hungry, it's hard not to take a bite! Good thing Rida is here with me to hand me a real candy bar instead, so I don't ruin my teeth! Being the geologist in training that I am, I was hoping you could help me figure out if it is Igneous, Sedimentary, or Metamorphic. Which one do you think it is?

Also, if you have extra time, enjoy this game about rocks and solids. Just follow the directions to grab a rock and drop it on the tester. Then make a mental hypothesis about whether it will sink or float and watch what happens! Let me know how it goes. :)