Cleaning and Stain Removal - Cleaning glass tiles

I make necklace pendants with glass tiles. I have bought from several sources and only one has really nice tiles. Most of the tiles have a cloudy film on them and I can't get it off. They are about an inch square. I have tried regular cleaning products, vinegar and have let them soak overnight. One supplier said it won't come off and refunded my money, but I would like to find a solution because it's hard to find clean tiles.

Any ideas?

Thanks.

Nancy

could it be a glazing the tile is supposed to have on it that is damaged or a defect in that batch...my first guess would of been to use an acid like the vinegar to clean.....