Carol, that is urate. Chameleons are like birds, they don't pee like humans. If you notice next time he defecates it will be a brown, followed by that white that you notice. Also, be sure to pay attention to that as it's a good indicator to wether or not he's getting what he needs. A brown fecal and white urate mean he's hydrated well. If that urate turns yellow, it means he's dehydrated.