Chrysoberyl, chrysocolla, chrysolite and chrysoprase. That’s a lot of gemstones with confusingly similar names. And then there’s chalcedony, which in my head I lump in with the four named above because of its “ch”.

It can be hard to keep them all straight. Do you know the differences between them?

It’s chrysolite I really want to talk about here but let’s get the others out of the way first.

Before we start, let me stress that I’m not a gemologist, and I’m not going to list chemical names or specify crystalline structures. As an antique jewellery dealer I’m interested in how stones look, how they react to light, and how they have been used in the jewels from the periods I deal in, broadly 1700 to about 1960.

I’ll begin with the last one I mentioned, chalcedony, because it appears in several semi-precious forms. These include agate, moss agate, carnelian (as it’s commonly called today, though in my years in the antique markets of London we called it cornelian) and onyx.

Pure chalcedony is white – it’s impurities that add the colour. One often sees white chalcedony in antique jewellery, along with pale blue, mauve and grey versions. It was always shaped and polished rather than faceted because of a special quality that is the result of its crystalline structure: translucence.

When at its best this translucence – and the accompanying distribution of colour – lends itself to large earrings. I’ve written before about how earrings are better than any other type of jewellery at showcasing the beauty of gemstones.

Let’s move on to chrysoprase, which is actually yet another type of chalcedony. It’s the green version, and can look very similar to jade. In the west it was at its height of popularity during the Art Deco period – as indeed was jade and all things oriental.

Late Georgian and early Victorian white chalcedony long-drop earrings were the inspiration for their later Art Deco chrysoprase counterparts, as seen in these examples I’ve previously sold (and kindly modelled for me by their new owners).

I’m not going to say much about chrysocolla, a blue-green stone sometimes confused with turquoise, because it isn’t common in the antique jewellery I sell. But I do admire the intense greenish blue of another, similar gemstone with a yet another similar name – chrysocolla chalcedony, also known as gem silica. Extra confusingly, it’s not a form of chrysocolla. It is a chalcedony, though, and top-grade gem silica can demand the highest prices of all the chalcedony variants.

Now on to chrysoberyl, a hard gemstone that is (again bewilderingly) not a beryl – the best-loved beryls are softer and more brittle emeralds and aquamarines. It appears in three main varieties.

The first is ordinary chrysoberyl, which is yellowish-green. The second is chrysoberyl cat’s eye which, when cut in cabochon shape, can display a strong band of opalescence reminiscent of a feline eye. This optical effect is known as “chatoyancy”, from the French “oeil de chat”. The third is the highly prized and extremely rare alexandrite, which has a similarly spectacular trick up its sleeve: it can change colour from green to red depending on the light.

And so finally we can move on to chrysolite, a name derived from the Greek and Latin words for “gold stone”.

Textbooks will tell you there is no such gemstone. Strictly, this is true. It’s is an archaic term that refers to a number of different gems that all display yellow and green hues. These include chrysoberyls, peridots, topazes, sapphires and tourmalines.

Because of this ambiguity, the word chrysolite is no longer used by gemologists. But I believe it has value.

Many antique dealers still use the term, myself included. We do this because it identifies stones of a distinct yellow green that were often seen in late Georgian and early to mid Victorian jewellery.

Then they seemed to disappear. It’s my guess that most of these stones were uniquely coloured peridots from a rich seam that was eventually mined out.

Infuriatingly, my valuer was unable to test the chrysolites set around a cabochon garnet in an opulent Holbeinesque necklet from about 1870 that I have for sale in my shop (see the photo at the top of this blog). The curvature of the large central stone prevented his equipment from getting a proper reading. This means my description for these beguiling beauties must remain, correctly and emphatically, “chrysolites”.