Oh Chalcedony!

In a poem that confused me in high school—many poems confused me in high school, and many still do—Edna St. Vincent Millay describes the pain of an old love affair as something ‘clear and diminished like a scene cut in cameo’:

‘O troubled forms, O early love unfortunate and hard
Time has estranged you into a jewel cold and pure; …
White against a ruddy cliff you stand, chalcedony on sard.’

—Edna St. Vincent Millay, The Cameo

What the hell were chalcedony and sard? Well, they were minerals, the white and red colors of a carved stone cameo. (In Millay’s meter, ‘chalcedony’ is to be pronounced with the accent on the second syllable, kal-seh-duh-nē.) But Millay, who was usually right about such things, got this one wrong. Red and white cameos are carved from a banded mineral called sardonyx. Sard is the red stuff, onyx the white. (Actually, most cameos are carved from seashells, some of which are called sardonyx shells. Confusing indeed.)

Sardonyx—two colors of chalcedony in alternating layers

And chalcedony? Chalcedony is the mother ship, the mineral family that includes sard and onyx and a host of other colorful stones, including jasper, agate, carnelian and chrysoprase. If a stone is pretty and you’re not sure what it is, it’s probably some kind of chalcedony. Which kind is a matter of debate—even mineralogists can’t agree on how to classify some of them. I tend to think of them all as agate, though I know this isn’t right.

Chalcedony is a microcrystalline form of quartz (silicon dioxide), meaning its crystal structure is too small to be seen with the unaided eye. You’re already familiar with quartzes that can grow visible crystals, like amethyst, citrine and rock crystal. These can be sparkly. Chalcedony, by contrast, has a waxy luster. Being quartz, it has a hardness of 6.5 to 7, so it can be carved and polished. It’s been used in jewelry for millennia, and I’ll bet you already own some. Rummaging through my jewelry drawers, I found quite a bit of it.

Blue chalcedony beads from the jewelry drawer
Blue chalcedony and ruby cufflinks for sale at 1stdibs.com

The beads above, for example, are blue chalcedony, one of the more upscale varieties. Blue chalcedony is often cut into cabochons and used in fine jewelry—like the cufflinks at left, inset with rubies and purchasable online for a pretty penny. Blue chalcedony, especially when it’s dark and translucent, almost glows; it really is a gemstone.

Its similarly-hued mineral cousin, blue lace agate, below right, is also used in fine jewelry. Blue lace agate was first discovered in the 1960s in Namibia, and it’s said to have a calming effect. Reader, has anyone ever tried to sell you a stone that has an agitating effect?

Blue lace agate

Anyhow, here’s what makes this stone an agate: it’s banded. Most agate formed as nodules in volcanic rock, where silica was deposited in layers, or bands. It’s these lovely, um, calming bands that give the stone its decorative quality. Agate is supposed to be at least partly translucent—but isn’t always.

Banded agate beads from Iraqi Kurdistan

The beads above, for example, are not translucent, but they’re definitely agate—quite old, originally from Iraq. I bought them from an Etsy shop in Thailand and had them strung into necklaces for the daughters of a close friend. I think it’s very possible that if this agate were sliced thinly, it would indeed be translucent, as in the bracelet below.

Scottish Victorian bracelet for sale on Etsy
Scottish Victorian agate, jasper and heliotrope brooch

I’m taken with this bracelet, as I am with most Scottish Victorian jewelry—see my recent post on the subject. Agate is used so copiously in such pieces that they’re referred to generically as Scottish agate jewelry. But not every stone in Scottish jewelry is agate. Take the brooch at right: The red stones with white bands are agate. So are the pinkish stones with wavy bands. But the speckled reddish stones are jasper, and the green ones are heliotrope, a/k/a bloodstone—magnification reveals telltale spatters of red. But hey, folks, they’re all chalcedony.

And so are these beauties, which I found in an old metal box with a butterfly stamped on it:

Moss agate and carnelian. Don’t they play nicely together?

The red stones are carnelian (also spelled cornelian), which may or may not be the same thing as sard. The green/red/white stones are moss agate. And no, they’re not banded. In fact, they’re not technically agate, but clear chalcedony with inclusions of hornblende. I think it’s time to stop worrying about nomenclature, don’t you?

Moss agate cufflinks by Bent Knudsen

I bought the moss agate cufflinks above a few years ago, having narrowly missed out on buying an entire bracelet made of these links by the Danish modernist Bent Knudsen. It’s a pity my husband hardly wears cufflinks anymore—most of his shirts have buttons at the cuffs. Which means he doesn’t get to wear these cufflinks either:

Jasper and gold cufflinks by the late Daphne Milne Groos

They’re chalcedony, of course. Jasper, to be precise. Jasper often has intriguing patterns in it, often in shades of red. I’d forgotten about these lovely things. I ought to get some shirts with French cuffs and wear them myself.

One final bauble from the jewelry drawer:

Early Victorian pietra dura brooch

The brooch above is an example of a technique called pietra dura, literally ‘hard stone’. It’s Italian, the sort of piece a young English or American woman might have brought home from her grand tour of the Continent in the 1840s. The lower parts of the wings are agate, or possibly onyx; the red trim and the speckled body are probably jasper. The green stones are malachite—another sort of mineral entirely. But to the artisan who put these stones together, they were not minerals but colors for his palette. The artisan was an artist. And artistry is what matters.

2 thoughts on “Oh Chalcedony!

  1. Hi Marcia, I have been enjoying your posts very much. Thank you! Also wanted to wish you a zisen Pesach! Warmly, Atara

    Sent from my iPhone



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