Seaglass is one of the very few cases of a valuable item being created from the actions of the environment on man-made litter.
The most common colors of sea glass are kelly green, brown, and clear. These colors come the bottles used by companies like Heineken, Sprite, Canada Dry, Clorox, Anheuser-Busch, and others. The clear or white glass comes from clear plates and glasses, windshields, windows, and assorted other sources.
Less common colors include jade, amber (from bottles for whiskey, medicine, spirits, and early Clorox bottles), golden amber (mostly used for spirit bottles), lime green (from soda bottles during the 1960s), forest green, and soft blue (from soda bottles, medicine bottles, ink bottles, and fruit jars from the late 1800s and early 1900s, windows, and windshields.) These colors are found about once for every 25 to 100 pieces of sea glass found.
Uncommon colors of sea glass include sea foam, which comes primarily from early to mid-1900s Coca-Cola, Dr Pepper, and RC Cola bottles, as well as beer bottles. Soft green colors could come from bottles that were used for ink, fruit, and baking soda. These colors are found once in every 50 to 100 pieces.
Purple sea glass is very uncommon, as is citron, opaque white (from milk bottles), cobalt and cornflower blue (from early Milk of Magnesia bottles, poison bottles, artwork, and Bromo-Seltzer and Vicks VapoRub containers), and aqua (from Ball Mason jars and 19th century glass bottles.) These colors are found once for every 200 to 1,000 pieces found.
Rare and extremely rare colors include pink (used for plates during the Great Depression), gray, teal (from Mateus wine bottles and other places), black (very dark green glass from as early as the 1700s, made into bottles for gin and other substances. Some black sea glass is found around Australia, originating from 1940s beer bottles. Its rarity is due to the obscure materials that were used with glass to make the bottles, which increased its rate of decomposition.), yellow (mostly from Vaseline containers and used in the Depression era), turquoise (from tableware and art glass), red (found once in every 5,000 pieces), and orange (the least common type of sea glass, found once in 10,000 pieces.) These colors are found once for every 1,000 to 10,000 pieces collected. "Black" sea glass is rarely found and often originates from pre-1860 glass that is actually dark olive green.
Sea glass can be found all over the world, but the beaches of the Northeast United States, Hawaii, Puerto Rico, Maine, Nova Scotia, The Chesapeake Bay, California, and Southern Spain are famous for sea glass. The best times to look are during spring tides and perigean and proxigean tides, and during the first low tide after a storm.
Sea glass collectors claim that the term "sea glass" should be reserved for authentic specimens, and artificial sea glass should be termed "craft glass".