I bought this for my 4-year-old son, along with a partitioned collection bin for storage, as a start to his new rock collection. He treats them with care and loves to "study" them, along with other rocks he now has. These thin slices are fun because he can hold them up to the sun or place them on top of a lit surface to look at the color rings and swirls. He uses a magnifying glass, too, and feels like a real scientist. I think it really helps for a kid to get his hands on science rather than just looking at pictures. Ours are quite colorful, and I really enjoy looking at them with him. They are maybe 1.5-2 inches long and we've got pink, purple, blue, orange, brown, etc. A good purchase!