Instructions
Look for the markings on the glass. Authentic Lalique glass is often marked, whereas pressed glass are left unmarked. The glass will be marked with "R Lalique," possibly including "France" and a specific model number.
Check the color of the glass. Lalique comes in red, amber, green and blue. Since red is the hardest color and form to work with, it is much sought after by most buyers and frequently duplicated by modern fakes. A real Lalique would cost around $8,000, whereas a Lalique-style vase (or fake ones) would be somewhere around $650 in price.
Examine the details of the glass's design. Authentic Lalique glass is known for its fine detail. A glass decanter, for example, has a frosted and bulbous figure that showcases its streamlined and delicate design. It has a fish pattern right at the bottom of the glass, while a rotunda-shaped container has female silhouettes that display Lalique's Art Deco style.
Check the glass material. Lalique is made of opalescent glass. You will be able to see its effect more in high-relief areas. It may be difficult to examine its material on thin walls.
Weigh the Lalique glass in your hands. Authentic Lalique glass is heavy, whereas fake ones are a lot lighter in comparison.