"I wish I was wearing my favourite t-shirt instead of the one I have on now," he said.
Jon waited a moment, but there was no flash. Studying the stone, he found that there was now a red glow eminating from somehwere inside it. The light was dull, barely more than an ember, but it was constant and didn't seem to be going anywhere. Jon wondered what it could mean.
He retrieved the second stone from his pocket to compare, and found that only the first one was glowing.
After some deliberation, he decided to make a wish on the second rock.