Purple sea glass... a collectors dream. Finding a gorgeous piece of purple glass on the beach will make any sea glass collector excited. There are two types of purple sea glass:
1) intentionally made art glass, and
2) accidentally made
The sea glass we’re talking about today is the latter; an unintentional color that is very rare indeed. It’s one of the few colors you can date without any other clues besides the color. Lavender sea glass was most likely made between 1880 and 1920, but it wasn’t originally lavender. Can you guess it’s original color?
If you guessed clear, you’re right. So what made it become purple? Much of the sand used in glass manufacturing contains traces of iron, and clear glass cannot be made without neutralizing the iron. Why? Because iron will usually cause the glass to be some shade of aqua, light green, blueish green color
So glass makers added something to the mixture — manganese. According to the Corning Museum of Glass, manganese has been used as a de-colorizer since as early as the second century B.C. Apparently, glass makers originally did not know that when they added manganese to their glass, the color would be altered by exposure to sunlight. This exposure to UV rays is what turns the glass varying shades of purple. The sun causes manganese to oxidize, forming manganese oxide and causing the color change.
This color of sea glass is very rare. If you find one on the beach, you have permission to do a happy dance because you most likely have found a piece of glass that is at least 100 years old.