Post History
A clear mineral crystal can be worked to a lens shape with enough time and effort. Quartz, sapphire and ruby are likely candidates. Ruby lenses were common on wand style barcode reader pens. Even...
Answer
A clear mineral crystal can be worked to a lens shape with enough time and effort. Quartz, sapphire and ruby are likely candidates. Ruby lenses were common on wand style barcode reader pens. Even...