Today's Rosarita is named after the borosiliate glass used in the refinining process for gold prior to the 1970's. The gold would not be absorbed into the glass which made it easier for extraction. One of the chemical reactions of this process created a rich, dark red material called 'slag' that lapidary artists and jewelers alike fell in love with. Today's technology is much more efficient and the newer process no longer creates the vibrant reds this vintage material is known for. The Rosarita you find on the market today is not that same material, but it is named after the slag that stole hearts.