Genuine vs. Artificial

Please Note: This is copyrighted material and copying or duplicating any portion of this document without permission is a violation of international copyright laws. This document was produced as a compilation between several of the original board members of NASGA including Richard LaMotte and Charles Peden.

Originating from discarded bottles and tableware, or glass from shipwrecks and household items lost in natural disasters. Originating from either a factory, workshop or rock tumbler (in rare occurrences people bring premature sea glass home to finish it off in a rock tumbler). Craft glass may be made from sheets of glass which are cut up and tossed into a rock tumbler or acid bath. Craft glass can also come from recycled glass bottles. Some who are a bit more particular will actually seek out old bottles which to then turn into tumbled craft glass.
Quantities of some colors are severely limited. Colors such as orange, red, yellow, cobalt blue, purple, turquoise, “black”, and Vaseline are very rare. Genuine sea glass in these colors is normally never sold by the pound. Nearly all colors are readily available in quantity and pricing between colors is fairly consistent. Since one does not cost more than the other to produce it’s a sure sign of artificial sea glass.

“Colorized” glass  has been altered using paint or coloring added to create the illusion of color. Can be genuine or tumbled glass, either way, it is not genuine authentic unaltered sea glass according to NASGA and the sea glass community.

Sea glass is often hydrated and may have a “frosty” surface, appearing crystalline in structure. Hydration is a slow process where the lime and soda in glass is leached out by the constant contact with water, leaving variable pitting on the surface of the glass. The soda and lime can combine with other elements to form tiny crystals in the surface of the glass. Many good specimens will sparkle in the light. It is impossible to duplicate this process without actually allowing nature to take its course over several years. To duplicate the hydration process that genuine beach sea glass undergoes, many manufacturers will etch the glass in an acid bath after tumbling it. Improperly rinsed, the glass may still contain some acid residue which can be toxic. Some large craft stores that carry tumbled craft glass caution you against using it in your aquarium and to avoid excessive handling. This type of tumbled glass is often used in the floral industry in vases to support flowers.
Small “C” shaped patterns may emerge on the surface of the beach sea glass and small hair line cracks may develop on some pieces. Etched glass has a satiny appearance and will be very uniform in its finish. It may be devoid of any small “C” shaped patterns on the surface, (which may occur on genuine beach sea glass.)  Improved techniques can also replicate the “C” shaped patterns, so take note of the other tell tale signs of fake sea glass, such as the shape or quantities available by the same seller.
Natural tumbling is often uneven on rocky shores, where a piece of sea glass got stuck with a portion of it still exposed. This process frequently produces shards that are triangular shape, and yet in some areas such as sandy beaches, the tumbling may be very even making them well rounded and nearly uniform in shape. Tumbled glass is often quite rough on the edges. If it is well worn the pieces in the lot will usually be small yet very similar in the overall degree of tumbling.
Sea glass may frequently be composed of identifiable bottle necks, bottle bottoms lettering and other unusual shapes and distinguishing features such as mug handles and so forth. Many times tumbled craft glass comes in large chunky amorphous shapes, and sometimes it comes as nearly uniform squares and triangles. If it is recycled glassware such as bottles, odds are that you will only find mass produced bottle necks or bottoms, nearly all of the glass will come from mass production and in any color.
Sea glass continues to go up in price as supplies dwindle (littering is discouraged) and more and more people become collectors. Tumbled craft glass has a market and the differences are easy to see up close. It pays to be informed and ask questions.


  • There are many sources to purchase sea glass, but fraud does exist and it pays to be an educated consumer when shopping for sea glass.
  • Ask before you buy: Just because the seller is advertising that they have beach sea glass, does not mean that the glass has ever been to a beach. Some sellers are simply uneducated in the differences between genuine sea glass and artificially tumbled craft glass. Some try to pass off craft glass as beach glass and there are plenty who sell the genuine article and spend hours searching for it.
  • Purchase loose sea glass, jewelry or products from NASGA members, who must abide by the NASGA mission to use only GENUINE sea glass in it’s natural state.   A list of NASGA members can be found here.
  • Though some locations do produce high volumes of natural sea glass, if pictures of many listings by the same seller show very uniform size, rare colors, or overly glossy appearance, it’s possible that tumbled glass could be misrepresented as genuine sea glass.
  • “Colorizing” is also a fairly new way to alter sea glass so buyer beware!   “Colorizing” is altering glass using paint or coloring added to create the illusion of color. Can be genuine or tumbled glass, either way, it is not genuine authentic unaltered sea glass according to NASGA and the sea glass community.   See photo below.
  • If the picture in the listing or the bag of sea glass shows very uniform color, with no variance in the hue from piece to piece, odds are that it is tumbled craft glass. Blurry, poorly-lit pictures are also a red flag.
  • Pricing is not a reliable indicator of authenticity, as some sellers price differently then others based upon supply and demand. That being said, if you see a pound of red advertised for $10.00, odds are that it is not genuine natural beach sea glass.
Glass that has been altered using paint or coloring added to create the illusion of color. Can be genuine or tumbled glass, either way, it is not genuine authentic unaltered sea glass.
In this photo, genuine beach found sea glass on the left and artificially tumbled craft glass on the right.
The same photo as above, with the artificially tumbled craft glass covered up.
Another photo of artificial tumbled “sea glass”.

NASGA bottle logo