The first "rock" is a synthetic, I believe. As it is more than likely made of plastic or ceramic, it shouldn't do any harm.
I have personally never used synthetic rocks. I'm lucky to have a wide variety of rock where I live in Nebraska. Pet shops rob people blind when it comes to rocks. Heck, I could supplement my income with the rocks out here. Shale, slate, redrock, petrified wood..............oodles of it.