Kids loved them!
Treasure hunt at birthday party was a hit. It was like an Easter egg hunt with plastic gems.  Hid them around the swingset. Kids like them because they are so big.  They are a hearty acrylic type plastic. They don't refract light like a glass or crystal gem might, but they are clear and colorful and impressive to kids.  They fill up the palm of a k/1 kid, about 1.5 inches across and a little less than an inch deep. The price was good.