Ellen and I actually had something similar to this happen to us:

Once the couch was extinguished, [Fire Prevention Officer] Gibson reached into a hole burnt into the sofa and found a glass gazing ball. Soon, sunlight shining through the ball burned two holes in the leg of his pants.

In our case Ellen had a very impressive crystal ball (well, it's probably glass, but still) sitting on the windowsill of our west-facing apartment. All through the first summer we lived there we were constantly bothered by the smell of smoke. We figured it was just the neighbors smoking. It was only after we'd bought a bookshelf and moved the books stacked next to the ball that we learned the truth. One book near the ball had a fingernail-sized hole burned nearly through it, and another's spine had been completely destroyed, a hole burned in nearly the size of a golf ball.

We moved the thing to the other side of the room on top of a video tape cabinet. Later that year Ajax the cat tried to jump to the top of that, knocking the ball off and nearly braining my sister-in-law who was sleeping on our floor that night*. We just put it away after that.