Beware Crystal Balls

I have had a crystal ball for a long time- possibly two years.  I decided to finally take it outside and try it out.  I took some pics of dandelions and the crystal ball wasn't really helping.  So I put it on the beach towel I had out so it wouldn't roll off of the table.  Then I worked on macro dandelion.  In less than a minute, I moved my camera and right next to me there was smoke coming from the towel!  The sun through the ball was starting a fire!  I have since found out that many people have had this experience.  So surprised that I have not heard of this!  Yikes!!