Ancient Roman iridescent glass dug up in Israel is now being featured in modern jewelry.

One of the jewelry designers told viewers of a late-night shopping channel that the thin layer of iridescence called “patina” was taken from the ancient glass and assembled flake by flake on a base used to create new jewelry.

A chemical reaction causes buried glass to form the iridescent layer. We have seen 1950s bottles buried in a damp location that show this type of iridescence. Artists have admired this glass iridescence since the early 1800s. In 1817, a man from Scotland patented a way to iridize glass, but the glass that collectors like today, the kind with a golden iridescence, was made by Ludwig Lobmeyr of Austria-Hungary in 1873.

Other glass artists, including Louis Comfort Tiffany, began making their own type of iridescent glass. Some of the factories that made gold iridescent glass and the date they started are: Glasfabrik Johann Loetz-Witwe (1890), Wilhelm Kralik Sohn (1890s), Tiffany (1896), Koloman Moser (1900), Quezal Art Glass Co. (1901) and Steuben Glass Co. (1903). Carnival glass, a less-expensive and very different-looking type of iridescent glass, was made after 1908.

Collectors and even experts often cannot identify the maker of a gold iridescent glass piece because the pieces are all so similar. And modern glassmakers can produce very similar glass pieces, too, so there is much confusion.

The most expensive and most popular is Tiffany gold glass.

I would like to know the age and make of my cast-iron toy gun. It’s marked “TG-27” and has a funny nub on the bottom and a short barrel. It probably opens at the grip. My brother repainted the entire gun to cover up rust.

Your toy gun is a cap gun made by the National Toy Co. The nub on the bottom of the grip lifts up to show where the caps should be loaded. Although the company didn’t officially incorporate until 1914, your cap gun likely dates from 1911. The company’s products were successful and sold in stores like FAO Schwarz. Since your cap gun is repainted, its value is very low.

Tip: Do not display carnival glass made before 1910 in direct sunlight. The glass, introduced in 1907, will turn purple or brown and its iridescent finish may fade.