Since anything babies play with is bound to be put into the mouth, toys should have smooth surfaces, and they should be easy to wash. There should be no sharp edges or detachable parts such as glass...
A slippery mineral
What is inside the pencil you use to write? It's often called "lead"---but it's not really lead at all. It's a mixture of clay and a soft, black mineral called graphite (GRAF yt). Some graphite is...