How To Tell the Difference: Is it Jet or Black Glass?

We’re going to take a look at a few of the more common types of black jewelry that were popular circa 1850-1900. During this Victorian time, black jewelry was not only fashionable but also  often worn during a time of mourning. Hence, you’ll sometimes hear it referred to as ‘mourning jewelry’.

One of the more popular types of jet jewelry was made by Whitby of England.  It is highly collectible and still brings a good price today.  However, many collectors find it difficult to tell the difference between jet, glass – and onyx  in spite of the fact that they each have very different characteristics.

In order to distinguish one from another, it helps to know a little about each one. We’ll take a quick look at the differences and then give you a few hints that may help you determine what you have.

Jet

Jet is considered to be a minor gemstone since it is a geological material. It is not considered a true mineral, but rather a mineraloid as it is derived from decaying wood under extreme pressure. Unlike diamonds which are crystalline, jet is similar in structure to the tree from which it comes. As such, genuine jet may show the texture or grain of the wood itself if the piece has a flat surface, i.e., flat backs of brooches, pins.

Jet is soft as limestone and easy to carve. This characteristic also makes it susceptible to chips. If chipped, the damage will typically be shell shaped. Look for this damage along the edges.

It can also be brought to a high polish and retain this polish for many years without showing any damage to the piece.  As previously mentioned, the finest jet pieces were produced in Whitby, England where at one time over 200 shops produced Victorian era jet jewelry.

Interestingly, during the 1920’s long jet bead necklaces were popular and young ‘flappers’ would wear multiple strings of jet beads from neck to waistline.

French Jet

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The fact that true jet held a high polish is one reason it was easily imitated using black glass. Glass ‘jet’ is often referred to as ‘French Jet’. During the hey-day of jet jewelry, most of the glass imitations were produced in Bohemia (Czech).

However, unlike the real thing, over time French jet tended to become dull, show surface scratches, get  chips along edges or under prongs – and in some cases it would even crack.

When shopping for ‘jet jewelry, look on the fastener for country of origin. French jet will most likely be marked ‘Bohemia’.

Onyx

Onyx is a variety of chalcedony (variety of quartz) and as such is considered a gemstone. Most chalcedony is banded in almost every color except some shades of blue or purple. However, never will you find it in a solid black. Onyx is chalcedony that has been artificially dyed black. In some cases, depending on the under lying colors, you may find the onyx to appear uneven in color.

How to tell the difference?

The best way to be sure of what you have is to check with either a gemologist or an experienced jeweler. However, if you’re looking for a few hints, the following may help out:

Glass:

  • Look for dullness, chips, scratches, cracks
  • Glass will be heavier than jet and cold to the touch

 Jet:

  • Lighter in weight and warm to the touch
  • Look for wood grain on the back of flat pieces
  • Damage, chips to jet will be ‘shell’ shaped
  • May induce an electric charge when rubbed . . . much like amber
  • Touch of a red hot needle should cause an odor to be emitted similar to coal (careful where you perform the test – don’t leave any unsightly holes)
  • Read more info at this link –  http://jmfelton.com/jetid1.htm

Onyx:

  • Harder than glass, so it can scratch glass (careful not to damage the jewelry piece)
  • Since onyx is banded chalcedony that has been dyed, look for imperfections in the color

 

If you would like more information on jet jewelry, antique jewelry or gemstone identification, check out our recommended reference books on Amazon.

 

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